From 5cda2a9b4bc537acea44576bc3cc3e6b9ff42bdc Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Thu, 10 Apr 2025 15:45:32 +0200
Subject: [PATCH 01/24] run all 'thread' tests on FreeBSD, and also on 32bit

---
 src/tools/miri/ci/ci.sh                           | 6 +++---
 src/tools/miri/src/shims/windows/foreign_items.rs | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/tools/miri/ci/ci.sh b/src/tools/miri/ci/ci.sh
index b690bd9cd2b97..755e02d02eca1 100755
--- a/src/tools/miri/ci/ci.sh
+++ b/src/tools/miri/ci/ci.sh
@@ -164,9 +164,9 @@ case $HOST_TARGET in
     # Partially supported targets (tier 2)
     BASIC="empty_main integer heap_alloc libc-mem vec string btreemap" # ensures we have the basics: pre-main code, system allocator
     UNIX="hello panic/panic panic/unwind concurrency/simple atomic libc-mem libc-misc libc-random env num_cpus" # the things that are very similar across all Unixes, and hence easily supported there
-    TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal $BASIC $UNIX time hashmap random threadname pthread fs libc-pipe concurrency sync
-    TEST_TARGET=i686-unknown-freebsd   run_tests_minimal $BASIC $UNIX time hashmap random threadname pthread fs libc-pipe
-    TEST_TARGET=aarch64-linux-android  run_tests_minimal $BASIC $UNIX time hashmap random sync concurrency thread epoll eventfd
+    TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal $BASIC $UNIX time hashmap random thread sync concurrency fs libc-pipe
+    TEST_TARGET=i686-unknown-freebsd   run_tests_minimal $BASIC $UNIX time hashmap random thread sync concurrency fs libc-pipe
+    TEST_TARGET=aarch64-linux-android  run_tests_minimal $BASIC $UNIX time hashmap random thread sync concurrency epoll eventfd
     TEST_TARGET=wasm32-wasip2          run_tests_minimal $BASIC wasm
     TEST_TARGET=wasm32-unknown-unknown run_tests_minimal no_std empty_main wasm # this target doesn't really have std
     TEST_TARGET=thumbv7em-none-eabihf  run_tests_minimal no_std
diff --git a/src/tools/miri/src/shims/windows/foreign_items.rs b/src/tools/miri/src/shims/windows/foreign_items.rs
index 7d97e333cd9b0..ba4da155fc4d9 100644
--- a/src/tools/miri/src/shims/windows/foreign_items.rs
+++ b/src/tools/miri/src/shims/windows/foreign_items.rs
@@ -65,7 +65,7 @@ fn win_get_full_path_name<'tcx>(path: &Path) -> InterpResult<'tcx, io::Result<Pa
     }
     // Otherwise we try to do something kind of close to what Windows does, but this is probably not
     // right in all cases.
-    let mut result: Vec<&[u8]> = vec![]; // will be a vecot of components, joined by `/`.
+    let mut result: Vec<&[u8]> = vec![]; // will be a vector of components, joined by `/`.
     let mut bytes = bytes; // the remaining bytes to process
     let mut stop = false;
     while !stop {

From 2d37173c237f9b5cdc7f8971879a2162265cba61 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Thu, 10 Apr 2025 14:46:39 +0000
Subject: [PATCH 02/24] Bump crossbeam-channel from 0.5.14 to 0.5.15

Bumps [crossbeam-channel](https://github.com/crossbeam-rs/crossbeam) from 0.5.14 to 0.5.15.
- [Release notes](https://github.com/crossbeam-rs/crossbeam/releases)
- [Changelog](https://github.com/crossbeam-rs/crossbeam/blob/master/CHANGELOG.md)
- [Commits](https://github.com/crossbeam-rs/crossbeam/compare/crossbeam-channel-0.5.14...crossbeam-channel-0.5.15)

---
updated-dependencies:
- dependency-name: crossbeam-channel
  dependency-version: 0.5.15
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>
---
 src/tools/miri/Cargo.lock | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/tools/miri/Cargo.lock b/src/tools/miri/Cargo.lock
index 0c6f4a3dd06e7..bbdcccdc17f2c 100644
--- a/src/tools/miri/Cargo.lock
+++ b/src/tools/miri/Cargo.lock
@@ -257,9 +257,9 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-channel"
-version = "0.5.14"
+version = "0.5.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "06ba6d68e24814cb8de6bb986db8222d3a027d15872cabc0d18817bc3c0e4471"
+checksum = "82b8f8f868b36967f9606790d1903570de9ceaf870a7bf9fbbd3016d636a2cb2"
 dependencies = [
  "crossbeam-utils",
 ]

From f243cb8861fc2def232e43b6acc2e2cd6867b89c Mon Sep 17 00:00:00 2001
From: Rune Tynan <runetynan@gmail.com>
Date: Wed, 9 Apr 2025 22:53:57 -0700
Subject: [PATCH 03/24] Implement RtlNtStatusToDosError and shim test for it

---
 .../miri/src/shims/windows/foreign_items.rs   | 19 +++++++++++++++++++
 .../miri/tests/pass-dep/shims/windows-fs.rs   | 11 ++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/tools/miri/src/shims/windows/foreign_items.rs b/src/tools/miri/src/shims/windows/foreign_items.rs
index 33b654042391d..0c4afc069e205 100644
--- a/src/tools/miri/src/shims/windows/foreign_items.rs
+++ b/src/tools/miri/src/shims/windows/foreign_items.rs
@@ -346,6 +346,25 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let last_error = this.get_last_error()?;
                 this.write_scalar(last_error, dest)?;
             }
+            "RtlNtStatusToDosError" => {
+                let [status] = this.check_shim(abi, sys_conv, link_name, args)?;
+                let status = this.read_scalar(status)?.to_u32()?;
+                let err = match status {
+                    // STATUS_MEDIA_WRITE_PROTECTED => ERROR_WRITE_PROTECT
+                    0xC00000A2 => 19,
+                    // STATUS_FILE_INVALID => ERROR_FILE_INVALID
+                    0xC0000098 => 1006,
+                    // STATUS_DISK_FULL => ERROR_DISK_FULL
+                    0xC000007F => 112,
+                    // STATUS_IO_DEVICE_ERROR => ERROR_IO_DEVICE
+                    0xC0000185 => 1117,
+                    // STATUS_ACCESS_DENIED => ERROR_ACCESS_DENIED
+                    0xC0000022 => 5,
+                    // Anything without an error code => ERROR_MR_MID_NOT_FOUND
+                    _ => 317,
+                };
+                this.write_scalar(Scalar::from_i32(err), dest)?;
+            }
 
             // Querying system information
             "GetSystemInfo" => {
diff --git a/src/tools/miri/tests/pass-dep/shims/windows-fs.rs b/src/tools/miri/tests/pass-dep/shims/windows-fs.rs
index 312df9eb115db..a015464dbde32 100644
--- a/src/tools/miri/tests/pass-dep/shims/windows-fs.rs
+++ b/src/tools/miri/tests/pass-dep/shims/windows-fs.rs
@@ -10,7 +10,9 @@ use std::ptr;
 mod utils;
 
 use windows_sys::Win32::Foundation::{
-    CloseHandle, ERROR_ALREADY_EXISTS, GENERIC_READ, GENERIC_WRITE, GetLastError,
+    CloseHandle, ERROR_ACCESS_DENIED, ERROR_ALREADY_EXISTS, ERROR_IO_DEVICE, GENERIC_READ,
+    GENERIC_WRITE, GetLastError, RtlNtStatusToDosError, STATUS_ACCESS_DENIED,
+    STATUS_IO_DEVICE_ERROR,
 };
 use windows_sys::Win32::Storage::FileSystem::{
     BY_HANDLE_FILE_INFORMATION, CREATE_ALWAYS, CREATE_NEW, CreateFileW, FILE_ATTRIBUTE_DIRECTORY,
@@ -26,6 +28,7 @@ fn main() {
         test_create_always_twice();
         test_open_always_twice();
         test_open_dir_reparse();
+        test_ntstatus_to_dos();
     }
 }
 
@@ -191,6 +194,12 @@ unsafe fn test_open_dir_reparse() {
     };
 }
 
+unsafe fn test_ntstatus_to_dos() {
+    // We won't test all combinations, just a couple common ones
+    assert_eq!(RtlNtStatusToDosError(STATUS_IO_DEVICE_ERROR), ERROR_IO_DEVICE);
+    assert_eq!(RtlNtStatusToDosError(STATUS_ACCESS_DENIED), ERROR_ACCESS_DENIED);
+}
+
 fn to_wide_cstr(path: &Path) -> Vec<u16> {
     let mut raw_path = path.as_os_str().encode_wide().collect::<Vec<_>>();
     raw_path.extend([0, 0]);

From 49cc8601821b614aa7a245dd37a837ec92192d3a Mon Sep 17 00:00:00 2001
From: LorrensP-2158466 <lorrens.pantelis@student.uhasselt.be>
Date: Fri, 11 Apr 2025 13:56:53 +0200
Subject: [PATCH 04/24] fix build fail on macos bacause of libffi-sys 2.3.0;
 This updates libffi to new major version

---
 src/tools/miri/Cargo.lock | 8 ++++----
 src/tools/miri/Cargo.toml | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/tools/miri/Cargo.lock b/src/tools/miri/Cargo.lock
index bbdcccdc17f2c..6f4bd3eab51a2 100644
--- a/src/tools/miri/Cargo.lock
+++ b/src/tools/miri/Cargo.lock
@@ -436,9 +436,9 @@ checksum = "c19937216e9d3aa9956d9bb8dfc0b0c8beb6058fc4f7a4dc4d850edf86a237d6"
 
 [[package]]
 name = "libffi"
-version = "3.2.0"
+version = "4.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ce826c243048e3d5cec441799724de52e2d42f820468431fc3fceee2341871e2"
+checksum = "4a9434b6fc77375fb624698d5f8c49d7e80b10d59eb1219afda27d1f824d4074"
 dependencies = [
  "libc",
  "libffi-sys",
@@ -446,9 +446,9 @@ dependencies = [
 
 [[package]]
 name = "libffi-sys"
-version = "2.3.0"
+version = "3.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f36115160c57e8529781b4183c2bb51fdc1f6d6d1ed345591d84be7703befb3c"
+checksum = "ead36a2496acfc8edd6cc32352110e9478ac5b9b5f5b9856ebd3d28019addb84"
 dependencies = [
  "cc",
 ]
diff --git a/src/tools/miri/Cargo.toml b/src/tools/miri/Cargo.toml
index e9ee19b793266..bb24e700e7388 100644
--- a/src/tools/miri/Cargo.toml
+++ b/src/tools/miri/Cargo.toml
@@ -37,7 +37,7 @@ features = ['unprefixed_malloc_on_supported_platforms']
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"
-libffi = "3.2.0"
+libffi = "4.0.0"
 libloading = "0.8"
 
 [target.'cfg(target_family = "windows")'.dependencies]

From 6788ce76c9f66b836a3b6a72d8b6df32627edecc Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Fri, 11 Apr 2025 13:47:52 +0200
Subject: [PATCH 05/24] Remove proc_macro::SourceFile::is_real().

---
 .../rustc_expand/src/proc_macro_server.rs     |  4 ----
 library/proc_macro/src/bridge/mod.rs          |  1 -
 library/proc_macro/src/lib.rs                 | 21 ++-----------------
 .../ui/proc-macro/auxiliary/span-api-tests.rs | 12 +----------
 tests/ui/proc-macro/span-api-tests.rs         |  2 --
 5 files changed, 3 insertions(+), 37 deletions(-)

diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index ee6306e396103..cd4ea8edd6fdf 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -689,10 +689,6 @@ impl server::SourceFile for Rustc<'_, '_> {
             _ => file.name.prefer_local().to_string(),
         }
     }
-
-    fn is_real(&mut self, file: &Self::SourceFile) -> bool {
-        file.is_real_file()
-    }
 }
 
 impl server::Span for Rustc<'_, '_> {
diff --git a/library/proc_macro/src/bridge/mod.rs b/library/proc_macro/src/bridge/mod.rs
index 1b5c221425ec6..d76e66521314b 100644
--- a/library/proc_macro/src/bridge/mod.rs
+++ b/library/proc_macro/src/bridge/mod.rs
@@ -86,7 +86,6 @@ macro_rules! with_api {
                 fn clone($self: &$S::SourceFile) -> $S::SourceFile;
                 fn eq($self: &$S::SourceFile, other: &$S::SourceFile) -> bool;
                 fn path($self: &$S::SourceFile) -> String;
-                fn is_real($self: &$S::SourceFile) -> bool;
             },
             Span {
                 fn debug($self: $S::Span) -> String;
diff --git a/library/proc_macro/src/lib.rs b/library/proc_macro/src/lib.rs
index f1cf0c5a2db7c..17beef2d47027 100644
--- a/library/proc_macro/src/lib.rs
+++ b/library/proc_macro/src/lib.rs
@@ -623,36 +623,19 @@ impl SourceFile {
     /// Gets the path to this source file.
     ///
     /// ### Note
-    /// If the code span associated with this `SourceFile` was generated by an external macro, this
-    /// macro, this might not be an actual path on the filesystem. Use [`is_real`] to check.
     ///
-    /// Also note that even if `is_real` returns `true`, if `--remap-path-prefix` was passed on
+    /// If `--remap-path-prefix` was passed on
     /// the command line, the path as given might not actually be valid.
-    ///
-    /// [`is_real`]: Self::is_real
     #[unstable(feature = "proc_macro_span", issue = "54725")]
     pub fn path(&self) -> PathBuf {
         PathBuf::from(self.0.path())
     }
-
-    /// Returns `true` if this source file is a real source file, and not generated by an external
-    /// macro's expansion.
-    #[unstable(feature = "proc_macro_span", issue = "54725")]
-    pub fn is_real(&self) -> bool {
-        // This is a hack until intercrate spans are implemented and we can have real source files
-        // for spans generated in external macros.
-        // https://github.com/rust-lang/rust/pull/43604#issuecomment-333334368
-        self.0.is_real()
-    }
 }
 
 #[unstable(feature = "proc_macro_span", issue = "54725")]
 impl fmt::Debug for SourceFile {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("SourceFile")
-            .field("path", &self.path())
-            .field("is_real", &self.is_real())
-            .finish()
+        f.debug_struct("SourceFile").field("path", &self.path()).finish()
     }
 }
 
diff --git a/tests/ui/proc-macro/auxiliary/span-api-tests.rs b/tests/ui/proc-macro/auxiliary/span-api-tests.rs
index 99db66ed6a94c..8853d793943f6 100644
--- a/tests/ui/proc-macro/auxiliary/span-api-tests.rs
+++ b/tests/ui/proc-macro/auxiliary/span-api-tests.rs
@@ -10,21 +10,11 @@ pub fn reemit(input: TokenStream) -> TokenStream {
     input.to_string().parse().unwrap()
 }
 
-#[proc_macro]
-pub fn assert_fake_source_file(input: TokenStream) -> TokenStream {
-    for tk in input {
-        let source_file = tk.span().source_file();
-        assert!(!source_file.is_real(), "Source file is real: {:?}", source_file);
-    }
-
-    "".parse().unwrap()
-}
-
 #[proc_macro]
 pub fn assert_source_file(input: TokenStream) -> TokenStream {
     for tk in input {
         let source_file = tk.span().source_file();
-        assert!(source_file.is_real(), "Source file is not real: {:?}", source_file);
+        assert!(!source_file.as_os_str().is_empty(), "No source file for span: {:?}", tk.span());
     }
 
     "".parse().unwrap()
diff --git a/tests/ui/proc-macro/span-api-tests.rs b/tests/ui/proc-macro/span-api-tests.rs
index ac42a7ea611ab..dd8589735b2e2 100644
--- a/tests/ui/proc-macro/span-api-tests.rs
+++ b/tests/ui/proc-macro/span-api-tests.rs
@@ -8,8 +8,6 @@ extern crate span_test_macros;
 
 extern crate span_api_tests;
 
-// FIXME(69775): Investigate `assert_fake_source_file`.
-
 use span_api_tests::{reemit, assert_source_file, macro_stringify};
 
 macro_rules! say_hello {

From 3962069982783ccf183e273a983b0c150c51d504 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Fri, 11 Apr 2025 14:35:00 +0200
Subject: [PATCH 06/24] Replace proc_macro::SourceFile by Span::{file,
 local_file}.

---
 .../rustc_expand/src/proc_macro_server.rs     | 47 ++++++++-------
 compiler/rustc_fluent_macro/src/fluent.rs     |  3 +
 library/proc_macro/src/bridge/client.rs       |  6 --
 library/proc_macro/src/bridge/mod.rs          | 10 +---
 library/proc_macro/src/bridge/server.rs       |  1 -
 library/proc_macro/src/lib.rs                 | 60 ++++++-------------
 tests/ui/proc-macro/auxiliary/expand-expr.rs  |  8 +--
 .../proc-macro/auxiliary/macro-only-syntax.rs |  2 +-
 .../ui/proc-macro/auxiliary/span-api-tests.rs |  5 +-
 tests/ui/proc-macro/span-api-tests.rs         | 12 ++--
 10 files changed, 61 insertions(+), 93 deletions(-)

diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index cd4ea8edd6fdf..0ab779945f21d 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -1,5 +1,4 @@
 use std::ops::{Bound, Range};
-use std::sync::Arc;
 
 use ast::token::IdentIsRaw;
 use pm::bridge::{
@@ -18,7 +17,7 @@ use rustc_parse::parser::Parser;
 use rustc_parse::{exp, new_parser_from_source_str, source_str_to_stream, unwrap_or_emit_fatal};
 use rustc_session::parse::ParseSess;
 use rustc_span::def_id::CrateNum;
-use rustc_span::{BytePos, FileName, Pos, SourceFile, Span, Symbol, sym};
+use rustc_span::{BytePos, FileName, Pos, Span, Symbol, sym};
 use smallvec::{SmallVec, smallvec};
 
 use crate::base::ExtCtxt;
@@ -467,7 +466,6 @@ impl<'a, 'b> Rustc<'a, 'b> {
 impl server::Types for Rustc<'_, '_> {
     type FreeFunctions = FreeFunctions;
     type TokenStream = TokenStream;
-    type SourceFile = Arc<SourceFile>;
     type Span = Span;
     type Symbol = Symbol;
 }
@@ -673,24 +671,6 @@ impl server::TokenStream for Rustc<'_, '_> {
     }
 }
 
-impl server::SourceFile for Rustc<'_, '_> {
-    fn eq(&mut self, file1: &Self::SourceFile, file2: &Self::SourceFile) -> bool {
-        Arc::ptr_eq(file1, file2)
-    }
-
-    fn path(&mut self, file: &Self::SourceFile) -> String {
-        match &file.name {
-            FileName::Real(name) => name
-                .local_path()
-                .expect("attempting to get a file path in an imported file in `proc_macro::SourceFile::path`")
-                .to_str()
-                .expect("non-UTF8 file path in `proc_macro::SourceFile::path`")
-                .to_string(),
-            _ => file.name.prefer_local().to_string(),
-        }
-    }
-}
-
 impl server::Span for Rustc<'_, '_> {
     fn debug(&mut self, span: Self::Span) -> String {
         if self.ecx.ecfg.span_debug {
@@ -700,8 +680,29 @@ impl server::Span for Rustc<'_, '_> {
         }
     }
 
-    fn source_file(&mut self, span: Self::Span) -> Self::SourceFile {
-        self.psess().source_map().lookup_char_pos(span.lo()).file
+    fn file(&mut self, span: Self::Span) -> String {
+        self.psess()
+            .source_map()
+            .lookup_char_pos(span.lo())
+            .file
+            .name
+            .prefer_remapped_unconditionaly()
+            .to_string()
+    }
+
+    fn local_file(&mut self, span: Self::Span) -> Option<String> {
+        self.psess()
+            .source_map()
+            .lookup_char_pos(span.lo())
+            .file
+            .name
+            .clone()
+            .into_local_path()
+            .map(|p| {
+                p.to_str()
+                    .expect("non-UTF8 file path in `proc_macro::SourceFile::path`")
+                    .to_string()
+            })
     }
 
     fn parent(&mut self, span: Self::Span) -> Option<Self::Span> {
diff --git a/compiler/rustc_fluent_macro/src/fluent.rs b/compiler/rustc_fluent_macro/src/fluent.rs
index b04fd1b48f7ad..c96bb48a0368c 100644
--- a/compiler/rustc_fluent_macro/src/fluent.rs
+++ b/compiler/rustc_fluent_macro/src/fluent.rs
@@ -25,7 +25,10 @@ fn invocation_relative_path_to_absolute(span: Span, path: &str) -> PathBuf {
         path.to_path_buf()
     } else {
         // `/a/b/c/foo/bar.rs` contains the current macro invocation
+        #[cfg(bootstrap)]
         let mut source_file_path = span.source_file().path();
+        #[cfg(not(bootstrap))]
+        let mut source_file_path = span.local_file().unwrap();
         // `/a/b/c/foo/`
         source_file_path.pop();
         // `/a/b/c/foo/../locales/en-US/example.ftl`
diff --git a/library/proc_macro/src/bridge/client.rs b/library/proc_macro/src/bridge/client.rs
index f6d4825c67b24..e7d547966a5d5 100644
--- a/library/proc_macro/src/bridge/client.rs
+++ b/library/proc_macro/src/bridge/client.rs
@@ -111,12 +111,6 @@ impl Clone for TokenStream {
     }
 }
 
-impl Clone for SourceFile {
-    fn clone(&self) -> Self {
-        self.clone()
-    }
-}
-
 impl Span {
     pub(crate) fn def_site() -> Span {
         Bridge::with(|bridge| bridge.globals.def_site)
diff --git a/library/proc_macro/src/bridge/mod.rs b/library/proc_macro/src/bridge/mod.rs
index d76e66521314b..75d82d7465404 100644
--- a/library/proc_macro/src/bridge/mod.rs
+++ b/library/proc_macro/src/bridge/mod.rs
@@ -81,15 +81,8 @@ macro_rules! with_api {
                     $self: $S::TokenStream
                 ) -> Vec<TokenTree<$S::TokenStream, $S::Span, $S::Symbol>>;
             },
-            SourceFile {
-                fn drop($self: $S::SourceFile);
-                fn clone($self: &$S::SourceFile) -> $S::SourceFile;
-                fn eq($self: &$S::SourceFile, other: &$S::SourceFile) -> bool;
-                fn path($self: &$S::SourceFile) -> String;
-            },
             Span {
                 fn debug($self: $S::Span) -> String;
-                fn source_file($self: $S::Span) -> $S::SourceFile;
                 fn parent($self: $S::Span) -> Option<$S::Span>;
                 fn source($self: $S::Span) -> $S::Span;
                 fn byte_range($self: $S::Span) -> Range<usize>;
@@ -97,6 +90,8 @@ macro_rules! with_api {
                 fn end($self: $S::Span) -> $S::Span;
                 fn line($self: $S::Span) -> usize;
                 fn column($self: $S::Span) -> usize;
+                fn file($self: $S::Span) -> String;
+                fn local_file($self: $S::Span) -> Option<String>;
                 fn join($self: $S::Span, other: $S::Span) -> Option<$S::Span>;
                 fn subspan($self: $S::Span, start: Bound<usize>, end: Bound<usize>) -> Option<$S::Span>;
                 fn resolved_at($self: $S::Span, at: $S::Span) -> $S::Span;
@@ -119,7 +114,6 @@ macro_rules! with_api_handle_types {
             'owned:
             FreeFunctions,
             TokenStream,
-            SourceFile,
 
             'interned:
             Span,
diff --git a/library/proc_macro/src/bridge/server.rs b/library/proc_macro/src/bridge/server.rs
index 97e5a603c3ac9..5beda7c3c96e5 100644
--- a/library/proc_macro/src/bridge/server.rs
+++ b/library/proc_macro/src/bridge/server.rs
@@ -82,7 +82,6 @@ with_api_handle_types!(define_server_handles);
 pub trait Types {
     type FreeFunctions: 'static;
     type TokenStream: 'static + Clone;
-    type SourceFile: 'static + Clone;
     type Span: 'static + Copy + Eq + Hash;
     type Symbol: 'static;
 }
diff --git a/library/proc_macro/src/lib.rs b/library/proc_macro/src/lib.rs
index 17beef2d47027..c46dcebedcab8 100644
--- a/library/proc_macro/src/lib.rs
+++ b/library/proc_macro/src/lib.rs
@@ -491,12 +491,6 @@ impl Span {
         Span(bridge::client::Span::mixed_site())
     }
 
-    /// The original source file into which this span points.
-    #[unstable(feature = "proc_macro_span", issue = "54725")]
-    pub fn source_file(&self) -> SourceFile {
-        SourceFile(self.0.source_file())
-    }
-
     /// The `Span` for the tokens in the previous macro expansion from which
     /// `self` was generated from, if any.
     #[unstable(feature = "proc_macro_span", issue = "54725")]
@@ -546,6 +540,25 @@ impl Span {
         self.0.column()
     }
 
+    /// The path to the source file in which this span occurs, for display purposes.
+    ///
+    /// This might not correspond to a valid file system path.
+    /// It might be remapped, or might be an artificial path such as `"<macro expansion>"`.
+    #[unstable(feature = "proc_macro_span", issue = "54725")]
+    pub fn file(&self) -> String {
+        self.0.file()
+    }
+
+    /// The path to the source file in which this span occurs on disk.
+    ///
+    /// This is the actual path on disk. It is unaffected by path remapping.
+    ///
+    /// This path should not be embedded in the output of the macro; prefer `file()` instead.
+    #[unstable(feature = "proc_macro_span", issue = "54725")]
+    pub fn local_file(&self) -> Option<PathBuf> {
+        self.0.local_file().map(|s| PathBuf::from(s))
+    }
+
     /// Creates a new span encompassing `self` and `other`.
     ///
     /// Returns `None` if `self` and `other` are from different files.
@@ -614,41 +627,6 @@ impl fmt::Debug for Span {
     }
 }
 
-/// The source file of a given `Span`.
-#[unstable(feature = "proc_macro_span", issue = "54725")]
-#[derive(Clone)]
-pub struct SourceFile(bridge::client::SourceFile);
-
-impl SourceFile {
-    /// Gets the path to this source file.
-    ///
-    /// ### Note
-    ///
-    /// If `--remap-path-prefix` was passed on
-    /// the command line, the path as given might not actually be valid.
-    #[unstable(feature = "proc_macro_span", issue = "54725")]
-    pub fn path(&self) -> PathBuf {
-        PathBuf::from(self.0.path())
-    }
-}
-
-#[unstable(feature = "proc_macro_span", issue = "54725")]
-impl fmt::Debug for SourceFile {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("SourceFile").field("path", &self.path()).finish()
-    }
-}
-
-#[unstable(feature = "proc_macro_span", issue = "54725")]
-impl PartialEq for SourceFile {
-    fn eq(&self, other: &Self) -> bool {
-        self.0.eq(&other.0)
-    }
-}
-
-#[unstable(feature = "proc_macro_span", issue = "54725")]
-impl Eq for SourceFile {}
-
 /// A single token or a delimited sequence of token trees (e.g., `[1, (), ..]`).
 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 #[derive(Clone)]
diff --git a/tests/ui/proc-macro/auxiliary/expand-expr.rs b/tests/ui/proc-macro/auxiliary/expand-expr.rs
index 78c9fa75d9ff2..14efc3c6b9f17 100644
--- a/tests/ui/proc-macro/auxiliary/expand-expr.rs
+++ b/tests/ui/proc-macro/auxiliary/expand-expr.rs
@@ -3,9 +3,10 @@
 
 extern crate proc_macro;
 
-use proc_macro::*;
 use std::str::FromStr;
 
+use proc_macro::*;
+
 // Flatten the TokenStream, removing any toplevel `Delimiter::None`s for
 // comparison.
 fn flatten(ts: TokenStream) -> Vec<TokenTree> {
@@ -136,9 +137,8 @@ pub fn check_expand_expr_file(ts: TokenStream) -> TokenStream {
         .to_string();
     assert_eq!(input_t, parse_t);
 
-    // Check that the literal matches `Span::call_site().source_file().path()`
-    let expect_t =
-        Literal::string(&Span::call_site().source_file().path().to_string_lossy()).to_string();
+    // Check that the literal matches `Span::call_site().file()`
+    let expect_t = Literal::string(&Span::call_site().file()).to_string();
     assert_eq!(input_t, expect_t);
 
     TokenStream::new()
diff --git a/tests/ui/proc-macro/auxiliary/macro-only-syntax.rs b/tests/ui/proc-macro/auxiliary/macro-only-syntax.rs
index 4971de284b760..11e1910288eee 100644
--- a/tests/ui/proc-macro/auxiliary/macro-only-syntax.rs
+++ b/tests/ui/proc-macro/auxiliary/macro-only-syntax.rs
@@ -79,7 +79,7 @@ fn check_useful_span(token: TokenTree, expected_filename: &str) {
     let span = token.span();
     assert!(span.column() < span.end().column());
 
-    let source_path = span.source_file().path();
+    let source_path = span.local_file().unwrap();
     let filename = source_path.components().last().unwrap();
     assert_eq!(filename, Component::Normal(expected_filename.as_ref()));
 }
diff --git a/tests/ui/proc-macro/auxiliary/span-api-tests.rs b/tests/ui/proc-macro/auxiliary/span-api-tests.rs
index 8853d793943f6..036f2e3ac3f5e 100644
--- a/tests/ui/proc-macro/auxiliary/span-api-tests.rs
+++ b/tests/ui/proc-macro/auxiliary/span-api-tests.rs
@@ -11,10 +11,9 @@ pub fn reemit(input: TokenStream) -> TokenStream {
 }
 
 #[proc_macro]
-pub fn assert_source_file(input: TokenStream) -> TokenStream {
+pub fn assert_local_file(input: TokenStream) -> TokenStream {
     for tk in input {
-        let source_file = tk.span().source_file();
-        assert!(!source_file.as_os_str().is_empty(), "No source file for span: {:?}", tk.span());
+        assert!(tk.span().local_file().is_some(), "No local file for span: {:?}", tk.span());
     }
 
     "".parse().unwrap()
diff --git a/tests/ui/proc-macro/span-api-tests.rs b/tests/ui/proc-macro/span-api-tests.rs
index dd8589735b2e2..792859ed05b16 100644
--- a/tests/ui/proc-macro/span-api-tests.rs
+++ b/tests/ui/proc-macro/span-api-tests.rs
@@ -8,24 +8,24 @@ extern crate span_test_macros;
 
 extern crate span_api_tests;
 
-use span_api_tests::{reemit, assert_source_file, macro_stringify};
+use span_api_tests::{reemit, assert_local_file, macro_stringify};
 
 macro_rules! say_hello {
     ($macname:ident) => ( $macname! { "Hello, world!" })
 }
 
-assert_source_file! { "Hello, world!" }
+assert_local_file! { "Hello, world!" }
 
-say_hello! { assert_source_file }
+say_hello! { assert_local_file }
 
 reemit_legacy! {
-    assert_source_file! { "Hello, world!" }
+    assert_local_file! { "Hello, world!" }
 }
 
-say_hello_extern! { assert_source_file }
+say_hello_extern! { assert_local_file }
 
 reemit! {
-    assert_source_file! { "Hello, world!" }
+    assert_local_file! { "Hello, world!" }
 }
 
 fn main() {

From 5113f5e6025a0742524aece5d69c87ef4257d338 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Fri, 11 Apr 2025 15:29:46 +0200
Subject: [PATCH 07/24] Update rust-analyzer for new proc_macro span api.

---
 .../src/server_impl/rust_analyzer_span.rs     | 29 +++++--------------
 .../src/server_impl/token_id.rs               | 22 ++++----------
 2 files changed, 13 insertions(+), 38 deletions(-)

diff --git a/src/tools/rust-analyzer/crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs b/src/tools/rust-analyzer/crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs
index 59293ee3f9659..80f6d85a3d05c 100644
--- a/src/tools/rust-analyzer/crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs
+++ b/src/tools/rust-analyzer/crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs
@@ -11,7 +11,7 @@ use std::{
 
 use intern::Symbol;
 use proc_macro::bridge::{self, server};
-use span::{FileId, Span, FIXUP_ERASED_FILE_AST_ID_MARKER};
+use span::{Span, FIXUP_ERASED_FILE_AST_ID_MARKER};
 use tt::{TextRange, TextSize};
 
 use crate::server_impl::{literal_kind_to_internal, token_stream::TokenStreamBuilder, TopSubtree};
@@ -27,10 +27,6 @@ mod tt {
 
 type TokenStream = crate::server_impl::TokenStream<Span>;
 
-#[derive(Copy, Clone, PartialEq, Eq, Debug)]
-pub struct SourceFile {
-    file_id: FileId,
-}
 pub struct FreeFunctions;
 
 pub struct RaSpanServer {
@@ -46,7 +42,6 @@ pub struct RaSpanServer {
 impl server::Types for RaSpanServer {
     type FreeFunctions = FreeFunctions;
     type TokenStream = TokenStream;
-    type SourceFile = SourceFile;
     type Span = Span;
     type Symbol = Symbol;
 }
@@ -245,25 +240,17 @@ impl server::TokenStream for RaSpanServer {
     }
 }
 
-impl server::SourceFile for RaSpanServer {
-    fn eq(&mut self, file1: &Self::SourceFile, file2: &Self::SourceFile) -> bool {
-        file1 == file2
-    }
-    fn path(&mut self, _file: &Self::SourceFile) -> String {
-        // FIXME
-        String::new()
-    }
-    fn is_real(&mut self, _file: &Self::SourceFile) -> bool {
-        true
-    }
-}
-
 impl server::Span for RaSpanServer {
     fn debug(&mut self, span: Self::Span) -> String {
         format!("{:?}", span)
     }
-    fn source_file(&mut self, span: Self::Span) -> Self::SourceFile {
-        SourceFile { file_id: span.anchor.file_id.file_id() }
+    fn file(&mut self, _: Self::Span) -> String {
+        // FIXME
+        String::new()
+    }
+    fn local_file(&mut self, _: Self::Span) -> Option<String> {
+        // FIXME
+        None
     }
     fn save_span(&mut self, _span: Self::Span) -> usize {
         // FIXME, quote is incompatible with third-party tools
diff --git a/src/tools/rust-analyzer/crates/proc-macro-srv/src/server_impl/token_id.rs b/src/tools/rust-analyzer/crates/proc-macro-srv/src/server_impl/token_id.rs
index 409cf3cc78134..4d7c7c46766b0 100644
--- a/src/tools/rust-analyzer/crates/proc-macro-srv/src/server_impl/token_id.rs
+++ b/src/tools/rust-analyzer/crates/proc-macro-srv/src/server_impl/token_id.rs
@@ -24,8 +24,6 @@ type Literal = tt::Literal;
 type Span = tt::TokenId;
 type TokenStream = crate::server_impl::TokenStream<Span>;
 
-#[derive(Clone)]
-pub struct SourceFile;
 pub struct FreeFunctions;
 
 pub struct TokenIdServer {
@@ -37,7 +35,6 @@ pub struct TokenIdServer {
 impl server::Types for TokenIdServer {
     type FreeFunctions = FreeFunctions;
     type TokenStream = TokenStream;
-    type SourceFile = SourceFile;
     type Span = Span;
     type Symbol = Symbol;
 }
@@ -223,24 +220,15 @@ impl server::TokenStream for TokenIdServer {
     }
 }
 
-impl server::SourceFile for TokenIdServer {
-    fn eq(&mut self, _file1: &Self::SourceFile, _file2: &Self::SourceFile) -> bool {
-        true
-    }
-    fn path(&mut self, _file: &Self::SourceFile) -> String {
-        String::new()
-    }
-    fn is_real(&mut self, _file: &Self::SourceFile) -> bool {
-        true
-    }
-}
-
 impl server::Span for TokenIdServer {
     fn debug(&mut self, span: Self::Span) -> String {
         format!("{:?}", span.0)
     }
-    fn source_file(&mut self, _span: Self::Span) -> Self::SourceFile {
-        SourceFile {}
+    fn file(&mut self, _span: Self::Span) -> String {
+        String::new()
+    }
+    fn local_file(&mut self, _span: Self::Span) -> Option<String> {
+        None
     }
     fn save_span(&mut self, _span: Self::Span) -> usize {
         0

From c4620021dc3d987a417abefc966996bf3ce4c617 Mon Sep 17 00:00:00 2001
From: The Miri Cronjob Bot <miri@cron.bot>
Date: Sat, 12 Apr 2025 05:00:08 +0000
Subject: [PATCH 08/24] Preparing for merge from rustc

---
 src/tools/miri/rust-version | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/tools/miri/rust-version b/src/tools/miri/rust-version
index d2b8b51473061..d1107e5150906 100644
--- a/src/tools/miri/rust-version
+++ b/src/tools/miri/rust-version
@@ -1 +1 @@
-7d7de5bf3c3cbf9c2c5bbc5cbfb9197a8a427d35
+1bc56185ee257ed829a0aea7abdc3b03c5fed887

From 59a3730169a4e4a34357b2c01b9134886ddf6512 Mon Sep 17 00:00:00 2001
From: The Miri Cronjob Bot <miri@cron.bot>
Date: Sat, 12 Apr 2025 05:08:28 +0000
Subject: [PATCH 09/24] fmt

---
 .../pass/issues/issue-134713-swap_nonoverlapping_untyped.rs     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/tools/miri/tests/pass/issues/issue-134713-swap_nonoverlapping_untyped.rs b/src/tools/miri/tests/pass/issues/issue-134713-swap_nonoverlapping_untyped.rs
index a1da60ce65c4d..27ea12398d88a 100644
--- a/src/tools/miri/tests/pass/issues/issue-134713-swap_nonoverlapping_untyped.rs
+++ b/src/tools/miri/tests/pass/issues/issue-134713-swap_nonoverlapping_untyped.rs
@@ -1,4 +1,4 @@
-use std::mem::{size_of, align_of};
+use std::mem::{align_of, size_of};
 
 // See <https://github.com/rust-lang/rust/issues/134713>
 

From 15a93c5683fa4a5c7a10b3e3385178ff0fd0fed6 Mon Sep 17 00:00:00 2001
From: Huang Qi <huangqi3@xiaomi.com>
Date: Sun, 13 Apr 2025 21:15:15 +0800
Subject: [PATCH 10/24] std/thread: Use default stack size from menuconfig for
 NuttX

* Update comments to clarify the usage of zero as an indication for default stack size configuration
* Adjust conditional compilation to reflect the changes in stack size handling for the NuttX platform

This change improves clarity and consistency in stack size configuration across platforms.

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>
---
 library/std/src/sys/pal/unix/thread.rs | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs
index 9078dd1c23166..4f1517b7ef420 100644
--- a/library/std/src/sys/pal/unix/thread.rs
+++ b/library/std/src/sys/pal/unix/thread.rs
@@ -8,14 +8,19 @@ use crate::sys::weak::weak;
 use crate::sys::{os, stack_overflow};
 use crate::time::Duration;
 use crate::{cmp, io, ptr};
-#[cfg(not(any(target_os = "l4re", target_os = "vxworks", target_os = "espidf")))]
+#[cfg(not(any(
+    target_os = "l4re",
+    target_os = "vxworks",
+    target_os = "espidf",
+    target_os = "nuttx"
+)))]
 pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
 #[cfg(target_os = "l4re")]
 pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
 #[cfg(target_os = "vxworks")]
 pub const DEFAULT_MIN_STACK_SIZE: usize = 256 * 1024;
-#[cfg(target_os = "espidf")]
-pub const DEFAULT_MIN_STACK_SIZE: usize = 0; // 0 indicates that the stack size configured in the ESP-IDF menuconfig system should be used
+#[cfg(any(target_os = "espidf", target_os = "nuttx"))]
+pub const DEFAULT_MIN_STACK_SIZE: usize = 0; // 0 indicates that the stack size configured in the ESP-IDF/NuttX menuconfig system should be used
 
 #[cfg(target_os = "fuchsia")]
 mod zircon {
@@ -52,10 +57,10 @@ impl Thread {
         let mut attr: mem::MaybeUninit<libc::pthread_attr_t> = mem::MaybeUninit::uninit();
         assert_eq!(libc::pthread_attr_init(attr.as_mut_ptr()), 0);
 
-        #[cfg(target_os = "espidf")]
+        #[cfg(any(target_os = "espidf", target_os = "nuttx"))]
         if stack > 0 {
             // Only set the stack if a non-zero value is passed
-            // 0 is used as an indication that the default stack size configured in the ESP-IDF menuconfig system should be used
+            // 0 is used as an indication that the default stack size configured in the ESP-IDF/NuttX menuconfig system should be used
             assert_eq!(
                 libc::pthread_attr_setstacksize(
                     attr.as_mut_ptr(),
@@ -65,7 +70,7 @@ impl Thread {
             );
         }
 
-        #[cfg(not(target_os = "espidf"))]
+        #[cfg(not(any(target_os = "espidf", target_os = "nuttx")))]
         {
             let stack_size = cmp::max(stack, min_stack_size(attr.as_ptr()));
 

From abce592029671a2f65e50901ad5fc55e42fdf930 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Fri, 11 Apr 2025 19:44:11 +1000
Subject: [PATCH 11/24] Use `Symbol` in `LateContext::get_associated_type`.

To avoid unnecessary interning.
---
 compiler/rustc_lint/src/context.rs                       | 9 +++++++--
 compiler/rustc_lint/src/deref_into_dyn_supertrait.rs     | 2 +-
 src/tools/clippy/clippy_lints/src/format_args.rs         | 2 +-
 src/tools/clippy/clippy_lints/src/len_zero.rs            | 2 +-
 .../clippy_lints/src/methods/iter_overeager_cloned.rs    | 2 +-
 .../clippy_lints/src/methods/unnecessary_iter_cloned.rs  | 2 +-
 .../clippy_lints/src/methods/unnecessary_to_owned.rs     | 6 +++---
 src/tools/clippy/clippy_utils/src/ty/mod.rs              | 2 +-
 8 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 16c9e08c78d38..a2d5ffe256d5c 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -855,11 +855,16 @@ impl<'tcx> LateContext<'tcx> {
         &self,
         self_ty: Ty<'tcx>,
         trait_id: DefId,
-        name: &str,
+        name: Symbol,
     ) -> Option<Ty<'tcx>> {
         let tcx = self.tcx;
         tcx.associated_items(trait_id)
-            .find_by_ident_and_kind(tcx, Ident::from_str(name), ty::AssocKind::Type, trait_id)
+            .find_by_ident_and_kind(
+                tcx,
+                Ident::with_dummy_span(name),
+                ty::AssocKind::Type,
+                trait_id,
+            )
             .and_then(|assoc| {
                 let proj = Ty::new_projection(tcx, assoc.def_id, [self_ty]);
                 tcx.try_normalize_erasing_regions(self.typing_env(), proj).ok()
diff --git a/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs b/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
index ec8f84415759f..5989ef9519cd7 100644
--- a/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
+++ b/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
@@ -69,7 +69,7 @@ impl<'tcx> LateLintPass<'tcx> for DerefIntoDynSupertrait {
             && let ty::Dynamic(data, _, ty::Dyn) = self_ty.kind()
             && let Some(self_principal) = data.principal()
             // `<T as Deref>::Target` is `dyn target_principal`
-            && let Some(target) = cx.get_associated_type(self_ty, did, "Target")
+            && let Some(target) = cx.get_associated_type(self_ty, did, sym::Target)
             && let ty::Dynamic(data, _, ty::Dyn) = target.kind()
             && let Some(target_principal) = data.principal()
             // `target_principal` is a supertrait of `t_principal`
diff --git a/src/tools/clippy/clippy_lints/src/format_args.rs b/src/tools/clippy/clippy_lints/src/format_args.rs
index 3862ff7921db8..06224f57c5c5b 100644
--- a/src/tools/clippy/clippy_lints/src/format_args.rs
+++ b/src/tools/clippy/clippy_lints/src/format_args.rs
@@ -550,7 +550,7 @@ impl<'tcx> FormatArgsExpr<'_, 'tcx> {
         // a `Target` that is in `self.ty_msrv_map`.
         if let Some(deref_trait_id) = self.cx.tcx.lang_items().deref_trait()
             && implements_trait(self.cx, ty, deref_trait_id, &[])
-            && let Some(target_ty) = self.cx.get_associated_type(ty, deref_trait_id, "Target")
+            && let Some(target_ty) = self.cx.get_associated_type(ty, deref_trait_id, sym::Target)
             && let Some(msrv) = self.ty_msrv_map.get(&target_ty)
             && msrv.is_none_or(|msrv| self.msrv.meets(self.cx, msrv))
         {
diff --git a/src/tools/clippy/clippy_lints/src/len_zero.rs b/src/tools/clippy/clippy_lints/src/len_zero.rs
index 72e22ae59d8f4..b01929747d69c 100644
--- a/src/tools/clippy/clippy_lints/src/len_zero.rs
+++ b/src/tools/clippy/clippy_lints/src/len_zero.rs
@@ -644,7 +644,7 @@ fn has_is_empty(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
                         && cx.tcx.get_diagnostic_item(sym::Deref).is_some_and(|deref_id| {
                             implements_trait(cx, ty, deref_id, &[])
                                 && cx
-                                    .get_associated_type(ty, deref_id, "Target")
+                                    .get_associated_type(ty, deref_id, sym::Target)
                                     .is_some_and(|deref_ty| ty_has_is_empty(cx, deref_ty, depth + 1))
                         }))
             },
diff --git a/src/tools/clippy/clippy_lints/src/methods/iter_overeager_cloned.rs b/src/tools/clippy/clippy_lints/src/methods/iter_overeager_cloned.rs
index f51bdc78f8a51..7bb625222ec0f 100644
--- a/src/tools/clippy/clippy_lints/src/methods/iter_overeager_cloned.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/iter_overeager_cloned.rs
@@ -48,7 +48,7 @@ pub(super) fn check<'tcx>(
         && let Some(method_id) = typeck.type_dependent_def_id(cloned_call.hir_id)
         && cx.tcx.trait_of_item(method_id) == Some(iter_id)
         && let cloned_recv_ty = typeck.expr_ty_adjusted(cloned_recv)
-        && let Some(iter_assoc_ty) = cx.get_associated_type(cloned_recv_ty, iter_id, "Item")
+        && let Some(iter_assoc_ty) = cx.get_associated_type(cloned_recv_ty, iter_id, sym::Item)
         && matches!(*iter_assoc_ty.kind(), ty::Ref(_, ty, _) if !is_copy(cx, ty))
     {
         if needs_into_iter
diff --git a/src/tools/clippy/clippy_lints/src/methods/unnecessary_iter_cloned.rs b/src/tools/clippy/clippy_lints/src/methods/unnecessary_iter_cloned.rs
index c0e0156858811..20cf35363d13f 100644
--- a/src/tools/clippy/clippy_lints/src/methods/unnecessary_iter_cloned.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/unnecessary_iter_cloned.rs
@@ -99,7 +99,7 @@ pub fn check_for_loop_iter(
             && let Some(into_iterator_trait_id) = cx.tcx.get_diagnostic_item(sym::IntoIterator)
             && let collection_ty = cx.typeck_results().expr_ty(collection)
             && implements_trait(cx, collection_ty, into_iterator_trait_id, &[])
-            && let Some(into_iter_item_ty) = cx.get_associated_type(collection_ty, into_iterator_trait_id, "Item")
+            && let Some(into_iter_item_ty) = cx.get_associated_type(collection_ty, into_iterator_trait_id, sym::Item)
             && iter_item_ty == into_iter_item_ty
             && let Some(collection_snippet) = collection.span.get_source_text(cx)
         {
diff --git a/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs b/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
index 62ba3012643ce..206b0a8ae3cd6 100644
--- a/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
@@ -153,7 +153,7 @@ fn check_addr_of_expr(
         }
         if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref)
             && implements_trait(cx, receiver_ty, deref_trait_id, &[])
-            && cx.get_associated_type(receiver_ty, deref_trait_id, "Target") == Some(target_ty)
+            && cx.get_associated_type(receiver_ty, deref_trait_id, sym::Target) == Some(target_ty)
             // Make sure that it's actually calling the right `.to_string()`, (#10033)
             // *or* this is a `Cow::into_owned()` call (which would be the wrong into_owned receiver (str != Cow)
             // but that's ok for Cow::into_owned specifically)
@@ -322,7 +322,7 @@ fn check_split_call_arg(cx: &LateContext<'_>, expr: &Expr<'_>, method_name: Symb
         // add `.as_ref()` to the suggestion.
         let as_ref = if is_type_lang_item(cx, cx.typeck_results().expr_ty(expr), LangItem::String)
             && let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref)
-            && cx.get_associated_type(cx.typeck_results().expr_ty(receiver), deref_trait_id, "Target")
+            && cx.get_associated_type(cx.typeck_results().expr_ty(receiver), deref_trait_id, sym::Target)
                 != Some(cx.tcx.types.str_)
         {
             ".as_ref()"
@@ -648,7 +648,7 @@ fn is_to_string_on_string_like<'a>(
         && let GenericArgKind::Type(ty) = generic_arg.unpack()
         && let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref)
         && let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef)
-        && (cx.get_associated_type(ty, deref_trait_id, "Target") == Some(cx.tcx.types.str_)
+        && (cx.get_associated_type(ty, deref_trait_id, sym::Target) == Some(cx.tcx.types.str_)
             || implements_trait(cx, ty, as_ref_trait_id, &[cx.tcx.types.str_.into()]))
     {
         true
diff --git a/src/tools/clippy/clippy_utils/src/ty/mod.rs b/src/tools/clippy/clippy_utils/src/ty/mod.rs
index 29cbf62c3d4c1..3779e2f306235 100644
--- a/src/tools/clippy/clippy_utils/src/ty/mod.rs
+++ b/src/tools/clippy/clippy_utils/src/ty/mod.rs
@@ -156,7 +156,7 @@ pub fn contains_ty_adt_constructor_opaque<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'
 pub fn get_iterator_item_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
     cx.tcx
         .get_diagnostic_item(sym::Iterator)
-        .and_then(|iter_did| cx.get_associated_type(ty, iter_did, "Item"))
+        .and_then(|iter_did| cx.get_associated_type(ty, iter_did, sym::Item))
 }
 
 /// Get the diagnostic name of a type, e.g. `sym::HashMap`. To check if a type

From ce2aa97cd647bdfcb5859489d93526622bb388a0 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Fri, 11 Apr 2025 06:28:59 +1000
Subject: [PATCH 12/24] Move `has_self` field to `hir::AssocKind::Fn`.

`hir::AssocItem` currently has a boolean `fn_has_self_parameter` field,
which is misplaced, because it's only relevant for associated fns, not
for associated consts or types. This commit moves it (and renames it) to
the `AssocKind::Fn` variant, where it belongs.

This requires introducing a new C-style enum, `AssocTag`, which is like
`AssocKind` but without the fields. This is because `AssocKind` values
are passed to various functions like `find_by_ident_and_kind` to
indicate what kind of associated item should be searched for, and having
to specify `has_self` isn't relevant there.

New methods:
- Predicates `AssocItem::is_fn` and `AssocItem::is_method`.
- `AssocItem::as_tag` which converts `AssocItem::kind` to `AssocTag`.

Removed `find_by_name_and_kinds`, which is unused.

`AssocItem::descr` can now distinguish between methods and associated
functions, which slightly improves some error messages.
---
 compiler/rustc_ast_lowering/src/delegation.rs |   2 +-
 .../src/diagnostics/conflict_errors.rs        |   2 +-
 .../rustc_codegen_cranelift/src/main_shim.rs  |   4 +-
 .../rustc_hir_analysis/src/check/check.rs     |   4 +-
 .../src/check/compare_impl_item.rs            |  14 +-
 compiler/rustc_hir_analysis/src/check/mod.rs  |   8 +-
 .../rustc_hir_analysis/src/check/wfcheck.rs   |   6 +-
 compiler/rustc_hir_analysis/src/collect.rs    |   6 +-
 .../src/collect/resolve_bound_vars.rs         |  16 +--
 .../src/collect/type_of/opaque.rs             |   4 +-
 .../src/hir_ty_lowering/bounds.rs             |  26 ++--
 .../src/hir_ty_lowering/errors.rs             |  57 ++++----
 .../src/hir_ty_lowering/mod.rs                | 124 ++++++++++--------
 .../rustc_hir_analysis/src/impl_wf_check.rs   |   2 +-
 compiler/rustc_hir_typeck/src/demand.rs       |  10 +-
 compiler/rustc_hir_typeck/src/expr.rs         |   4 +-
 .../rustc_hir_typeck/src/fn_ctxt/checks.rs    |   5 +-
 compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs  |   2 +-
 compiler/rustc_hir_typeck/src/method/mod.rs   |   2 +-
 compiler/rustc_hir_typeck/src/method/probe.rs |  15 +--
 .../rustc_hir_typeck/src/method/suggest.rs    |  27 ++--
 compiler/rustc_lint/src/context.rs            |   7 +-
 compiler/rustc_metadata/src/rmeta/decoder.rs  |  11 +-
 compiler/rustc_metadata/src/rmeta/encoder.rs  |   2 +-
 compiler/rustc_middle/src/mir/mod.rs          |   4 +-
 compiler/rustc_middle/src/ty/adjustment.rs    |   4 +-
 compiler/rustc_middle/src/ty/assoc.rs         |  62 +++++----
 compiler/rustc_middle/src/ty/instance.rs      |   2 +-
 compiler/rustc_middle/src/ty/mod.rs           |   2 +-
 compiler/rustc_middle/src/ty/util.rs          |   4 +-
 .../src/builder/matches/test.rs               |   2 +-
 compiler/rustc_mir_transform/src/shim.rs      |   2 +-
 .../src/mono_checks/move_check.rs             |   4 +-
 .../rustc_resolve/src/late/diagnostics.rs     |   2 +-
 .../cfi/typeid/itanium_cxx_abi/transform.rs   |   2 +-
 .../rustc_smir/src/rustc_smir/convert/ty.rs   |   5 +-
 .../rustc_smir/src/stable_mir/mir/pretty.rs   |   3 +-
 compiler/rustc_smir/src/stable_mir/ty.rs      |   6 +-
 .../src/error_reporting/infer/mod.rs          |   8 +-
 .../trait_impl_difference.rs                  |   2 +-
 .../infer/nice_region_error/util.rs           |   2 +-
 .../error_reporting/infer/note_and_explain.rs |   2 +-
 .../src/error_reporting/traits/ambiguity.rs   |   2 +-
 .../src/error_reporting/traits/suggestions.rs |   2 +-
 .../src/traits/dyn_compatibility.rs           |   4 +-
 .../src/traits/vtable.rs                      |   6 +-
 compiler/rustc_ty_utils/src/assoc.rs          |  20 ++-
 src/librustdoc/clean/inline.rs                |  12 +-
 src/librustdoc/clean/mod.rs                   |   4 +-
 .../src/bool_assert_comparison.rs             |   2 +-
 src/tools/clippy/clippy_lints/src/len_zero.rs |  11 +-
 .../src/methods/needless_collect.rs           |   4 +-
 .../clippy_lints/src/methods/or_fun_call.rs   |   2 +-
 .../src/needless_borrows_for_generic_args.rs  |   2 +-
 .../clippy_lints/src/same_name_method.rs      |   3 +-
 .../src/unconditional_recursion.rs            |   4 +-
 .../clippy/clippy_lints/src/unused_self.rs    |   2 +-
 src/tools/clippy/clippy_utils/src/ty/mod.rs   |   6 +-
 .../impl_bounds.stderr                        |   4 +-
 .../normalize/normalize-param-env-2.stderr    |   4 +-
 60 files changed, 288 insertions(+), 284 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index 2296b05f69b4c..93c627f64c967 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -85,7 +85,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     .delegation_fn_sigs
                     .get(&local_def_id)
                     .is_some_and(|sig| sig.has_self),
-                None => self.tcx.associated_item(def_id).fn_has_self_parameter,
+                None => self.tcx.associated_item(def_id).is_method(),
             },
             _ => span_bug!(span, "unexpected DefKind for delegation item"),
         }
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 8a8ecc3b96e3c..fe6dff7ff1b63 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -647,7 +647,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     && tc.polarity() == ty::PredicatePolarity::Positive
                     && supertrait_def_ids(tcx, tc.def_id())
                         .flat_map(|trait_did| tcx.associated_items(trait_did).in_definition_order())
-                        .any(|item| item.fn_has_self_parameter)
+                        .any(|item| item.is_method())
             })
         }) {
             return None;
diff --git a/compiler/rustc_codegen_cranelift/src/main_shim.rs b/compiler/rustc_codegen_cranelift/src/main_shim.rs
index 3b48adb7e918a..6eef97c14dd28 100644
--- a/compiler/rustc_codegen_cranelift/src/main_shim.rs
+++ b/compiler/rustc_codegen_cranelift/src/main_shim.rs
@@ -1,6 +1,6 @@
 use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
 use rustc_hir::LangItem;
-use rustc_middle::ty::{AssocKind, GenericArg};
+use rustc_middle::ty::{AssocTag, GenericArg};
 use rustc_session::config::EntryFnType;
 use rustc_span::{DUMMY_SP, Ident};
 
@@ -107,7 +107,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     .find_by_ident_and_kind(
                         tcx,
                         Ident::from_str("report"),
-                        AssocKind::Fn,
+                        AssocTag::Fn,
                         termination_trait,
                     )
                     .unwrap();
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index f50746dd18d6d..c2706a1d4013e 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -443,7 +443,7 @@ fn best_definition_site_of_opaque<'tcx>(
             let impl_def_id = tcx.local_parent(parent);
             for assoc in tcx.associated_items(impl_def_id).in_definition_order() {
                 match assoc.kind {
-                    ty::AssocKind::Const | ty::AssocKind::Fn => {
+                    ty::AssocKind::Const | ty::AssocKind::Fn { .. } => {
                         if let ControlFlow::Break(span) = locator.check(assoc.def_id.expect_local())
                         {
                             return Some(span);
@@ -942,7 +942,7 @@ fn check_impl_items_against_trait<'tcx>(
 
         if res.is_ok() {
             match ty_impl_item.kind {
-                ty::AssocKind::Fn => {
+                ty::AssocKind::Fn { .. } => {
                     compare_impl_item::refine::check_refining_return_position_impl_trait_in_trait(
                         tcx,
                         ty_impl_item,
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 29a9931696ffa..7dfdf1ae237d9 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -43,7 +43,7 @@ pub(super) fn compare_impl_item(
     debug!(?impl_trait_ref);
 
     match impl_item.kind {
-        ty::AssocKind::Fn => compare_impl_method(tcx, impl_item, trait_item, impl_trait_ref),
+        ty::AssocKind::Fn { .. } => compare_impl_method(tcx, impl_item, trait_item, impl_trait_ref),
         ty::AssocKind::Type => compare_impl_ty(tcx, impl_item, trait_item, impl_trait_ref),
         ty::AssocKind::Const => compare_impl_const(tcx, impl_item, trait_item, impl_trait_ref),
     }
@@ -1036,7 +1036,7 @@ fn report_trait_method_mismatch<'tcx>(
     );
     match &terr {
         TypeError::ArgumentMutability(0) | TypeError::ArgumentSorts(_, 0)
-            if trait_m.fn_has_self_parameter =>
+            if trait_m.is_method() =>
         {
             let ty = trait_sig.inputs()[0];
             let sugg = get_self_string(ty, |ty| ty == impl_trait_ref.self_ty());
@@ -1255,7 +1255,7 @@ fn compare_self_type<'tcx>(
         get_self_string(self_arg_ty, can_eq_self)
     };
 
-    match (trait_m.fn_has_self_parameter, impl_m.fn_has_self_parameter) {
+    match (trait_m.is_method(), impl_m.is_method()) {
         (false, false) | (true, true) => {}
 
         (false, true) => {
@@ -1363,7 +1363,7 @@ fn compare_number_of_generics<'tcx>(
     let mut err_occurred = None;
     for (kind, trait_count, impl_count) in matchings {
         if impl_count != trait_count {
-            let arg_spans = |kind: ty::AssocKind, generics: &hir::Generics<'_>| {
+            let arg_spans = |item: &ty::AssocItem, generics: &hir::Generics<'_>| {
                 let mut spans = generics
                     .params
                     .iter()
@@ -1373,7 +1373,7 @@ fn compare_number_of_generics<'tcx>(
                         } => {
                             // A fn can have an arbitrary number of extra elided lifetimes for the
                             // same signature.
-                            !matches!(kind, ty::AssocKind::Fn)
+                            !item.is_fn()
                         }
                         _ => true,
                     })
@@ -1386,7 +1386,7 @@ fn compare_number_of_generics<'tcx>(
             };
             let (trait_spans, impl_trait_spans) = if let Some(def_id) = trait_.def_id.as_local() {
                 let trait_item = tcx.hir_expect_trait_item(def_id);
-                let arg_spans: Vec<Span> = arg_spans(trait_.kind, trait_item.generics);
+                let arg_spans: Vec<Span> = arg_spans(&trait_, trait_item.generics);
                 let impl_trait_spans: Vec<Span> = trait_item
                     .generics
                     .params
@@ -1412,7 +1412,7 @@ fn compare_number_of_generics<'tcx>(
                     _ => None,
                 })
                 .collect();
-            let spans = arg_spans(impl_.kind, impl_item.generics);
+            let spans = arg_spans(&impl_, impl_item.generics);
             let span = spans.first().copied();
 
             let mut err = tcx.dcx().struct_span_err(
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index 30921b6f055d5..523db9440a41e 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -407,14 +407,14 @@ fn fn_sig_suggestion<'tcx>(
         .enumerate()
         .map(|(i, ty)| {
             Some(match ty.kind() {
-                ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
+                ty::Param(_) if assoc.is_method() && i == 0 => "self".to_string(),
                 ty::Ref(reg, ref_ty, mutability) if i == 0 => {
                     let reg = format!("{reg} ");
                     let reg = match &reg[..] {
                         "'_ " | " " => "",
                         reg => reg,
                     };
-                    if assoc.fn_has_self_parameter {
+                    if assoc.is_method() {
                         match ref_ty.kind() {
                             ty::Param(param) if param.name == kw::SelfUpper => {
                                 format!("&{}{}self", reg, mutability.prefix_str())
@@ -427,7 +427,7 @@ fn fn_sig_suggestion<'tcx>(
                     }
                 }
                 _ => {
-                    if assoc.fn_has_self_parameter && i == 0 {
+                    if assoc.is_method() && i == 0 {
                         format!("self: {ty}")
                     } else {
                         format!("_: {ty}")
@@ -489,7 +489,7 @@ fn suggestion_signature<'tcx>(
     );
 
     match assoc.kind {
-        ty::AssocKind::Fn => fn_sig_suggestion(
+        ty::AssocKind::Fn { .. } => fn_sig_suggestion(
             tcx,
             tcx.liberate_late_bound_regions(
                 assoc.def_id,
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index 6292d03bf6ac9..af7830fd6642a 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -432,7 +432,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
 
                 let item_required_bounds = match tcx.associated_item(item_def_id).kind {
                     // In our example, this corresponds to `into_iter` method
-                    ty::AssocKind::Fn => {
+                    ty::AssocKind::Fn { .. } => {
                         // For methods, we check the function signature's return type for any GATs
                         // to constrain. In the `into_iter` case, we see that the return type
                         // `Self::Iter<'a>` is a GAT we want to gather any potential missing bounds from.
@@ -1089,7 +1089,7 @@ fn check_associated_item(
                 );
                 Ok(())
             }
-            ty::AssocKind::Fn => {
+            ty::AssocKind::Fn { .. } => {
                 let sig = tcx.fn_sig(item.def_id).instantiate_identity();
                 let hir_sig = sig_if_method.expect("bad signature for method");
                 check_fn_or_method(
@@ -1716,7 +1716,7 @@ fn check_method_receiver<'tcx>(
 ) -> Result<(), ErrorGuaranteed> {
     let tcx = wfcx.tcx();
 
-    if !method.fn_has_self_parameter {
+    if !method.is_method() {
         return Ok(());
     }
 
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index deded6904d484..4520fbe352cea 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -44,7 +44,7 @@ use rustc_trait_selection::traits::ObligationCtxt;
 use tracing::{debug, instrument};
 
 use crate::errors;
-use crate::hir_ty_lowering::errors::assoc_kind_str;
+use crate::hir_ty_lowering::errors::assoc_tag_str;
 use crate::hir_ty_lowering::{FeedConstTy, HirTyLowerer, RegionInferReason};
 
 pub(crate) mod dump;
@@ -450,7 +450,7 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
         item_def_id: DefId,
         item_segment: &rustc_hir::PathSegment<'tcx>,
         poly_trait_ref: ty::PolyTraitRef<'tcx>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, ty::GenericArgsRef<'tcx>), ErrorGuaranteed> {
         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
             let item_args = self.lowerer().lower_generic_args_of_assoc_item(
@@ -525,7 +525,7 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
                 inferred_sugg,
                 bound,
                 mpart_sugg,
-                what: assoc_kind_str(kind),
+                what: assoc_tag_str(assoc_tag),
             }))
         }
     }
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 9bcda35ee87ad..1c477755e5ac6 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -1811,7 +1811,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                         self.tcx,
                         type_def_id,
                         constraint.ident,
-                        ty::AssocKind::Fn,
+                        ty::AssocTag::Fn,
                     ) {
                     bound_vars.extend(
                         self.tcx
@@ -1843,7 +1843,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                     self.tcx,
                     type_def_id,
                     constraint.ident,
-                    ty::AssocKind::Type,
+                    ty::AssocTag::Type,
                 )
                 .map(|(bound_vars, _)| bound_vars);
                 self.with(scope, |this| {
@@ -1875,13 +1875,13 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
         assoc_ident: Ident,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Option<(Vec<ty::BoundVariableKind>, &'tcx ty::AssocItem)> {
         let trait_defines_associated_item_named = |trait_def_id: DefId| {
             tcx.associated_items(trait_def_id).find_by_ident_and_kind(
                 tcx,
                 assoc_ident,
-                assoc_kind,
+                assoc_tag,
                 trait_def_id,
             )
         };
@@ -1894,8 +1894,8 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             let Some((def_id, bound_vars)) = stack.pop() else {
                 break None;
             };
-            // See issue #83753. If someone writes an associated type on a non-trait, just treat it as
-            // there being no supertrait HRTBs.
+            // See issue #83753. If someone writes an associated type on a non-trait, just treat it
+            // as there being no supertrait HRTBs.
             match tcx.def_kind(def_id) {
                 DefKind::Trait | DefKind::TraitAlias | DefKind::Impl { .. } => {}
                 _ => break None,
@@ -2067,7 +2067,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                                     self.tcx,
                                     trait_def_id,
                                     item_segment.ident,
-                                    ty::AssocKind::Fn,
+                                    ty::AssocTag::Fn,
                                 )
                             });
 
@@ -2112,7 +2112,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                             self.tcx,
                             trait_def_id,
                             item_segment.ident,
-                            ty::AssocKind::Fn,
+                            ty::AssocTag::Fn,
                         ) else {
                             return;
                         };
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index 772197a53ace1..f06636447194a 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -32,7 +32,9 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
     for &assoc_id in tcx.associated_item_def_ids(impl_def_id) {
         let assoc = tcx.associated_item(assoc_id);
         match assoc.kind {
-            ty::AssocKind::Const | ty::AssocKind::Fn => locator.check(assoc_id.expect_local()),
+            ty::AssocKind::Const | ty::AssocKind::Fn { .. } => {
+                locator.check(assoc_id.expect_local())
+            }
             // Associated types don't have bodies, so they can't constrain hidden types
             ty::AssocKind::Type => {}
         }
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
index 24d05b49861c5..bf91eb1b8fdac 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -431,16 +431,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     ) -> Result<(), ErrorGuaranteed> {
         let tcx = self.tcx();
 
-        let assoc_kind = if constraint.gen_args.parenthesized
+        let assoc_tag = if constraint.gen_args.parenthesized
             == hir::GenericArgsParentheses::ReturnTypeNotation
         {
-            ty::AssocKind::Fn
+            ty::AssocTag::Fn
         } else if let hir::AssocItemConstraintKind::Equality { term: hir::Term::Const(_) } =
             constraint.kind
         {
-            ty::AssocKind::Const
+            ty::AssocTag::Const
         } else {
-            ty::AssocKind::Type
+            ty::AssocTag::Type
         };
 
         // Given something like `U: Trait<T = X>`, we want to produce a predicate like
@@ -453,7 +453,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         //     trait SuperTrait<A> { type T; }
         let candidate = if self.probe_trait_that_defines_assoc_item(
             trait_ref.def_id(),
-            assoc_kind,
+            assoc_tag,
             constraint.ident,
         ) {
             // Simple case: The assoc item is defined in the current trait.
@@ -464,7 +464,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             self.probe_single_bound_for_assoc_item(
                 || traits::supertraits(tcx, trait_ref),
                 AssocItemQSelf::Trait(trait_ref.def_id()),
-                assoc_kind,
+                assoc_tag,
                 constraint.ident,
                 path_span,
                 Some(constraint),
@@ -474,7 +474,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let assoc_item = self
             .probe_assoc_item(
                 constraint.ident,
-                assoc_kind,
+                assoc_tag,
                 hir_ref_id,
                 constraint.span,
                 candidate.def_id(),
@@ -493,7 +493,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             })
             .or_insert(constraint.span);
 
-        let projection_term = if let ty::AssocKind::Fn = assoc_kind {
+        let projection_term = if let ty::AssocTag::Fn = assoc_tag {
             let bound_vars = tcx.late_bound_vars(constraint.hir_id);
             ty::Binder::bind_with_vars(
                 self.lower_return_type_notation_ty(candidate, assoc_item.def_id, path_span)?.into(),
@@ -542,7 +542,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         };
 
         match constraint.kind {
-            hir::AssocItemConstraintKind::Equality { .. } if let ty::AssocKind::Fn = assoc_kind => {
+            hir::AssocItemConstraintKind::Equality { .. } if let ty::AssocTag::Fn = assoc_tag => {
                 return Err(self.dcx().emit_err(crate::errors::ReturnTypeNotationEqualityBound {
                     span: constraint.span,
                 }));
@@ -679,7 +679,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         trait_def_id,
                         hir_ty.span,
                         item_segment,
-                        ty::AssocKind::Type,
+                        ty::AssocTag::Type,
                     );
                     return Ty::new_error(tcx, guar);
                 };
@@ -771,7 +771,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         )
                     },
                     AssocItemQSelf::SelfTyAlias,
-                    ty::AssocKind::Fn,
+                    ty::AssocTag::Fn,
                     assoc_ident,
                     span,
                     None,
@@ -783,7 +783,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             ) => self.probe_single_ty_param_bound_for_assoc_item(
                 param_did.expect_local(),
                 qself.span,
-                ty::AssocKind::Fn,
+                ty::AssocTag::Fn,
                 assoc_ident,
                 span,
             )?,
@@ -823,7 +823,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let trait_def_id = bound.def_id();
         let assoc_ty = self
-            .probe_assoc_item(assoc_ident, ty::AssocKind::Fn, qpath_hir_id, span, trait_def_id)
+            .probe_assoc_item(assoc_ident, ty::AssocTag::Fn, qpath_hir_id, span, trait_def_id)
             .expect("failed to find associated type");
 
         Ok((bound, assoc_ty.def_id))
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 5a0524d33fdea..4f8d5471b6f4d 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -116,7 +116,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         &self,
         all_candidates: impl Fn() -> I,
         qself: AssocItemQSelf,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
         assoc_ident: Ident,
         span: Span,
         constraint: Option<&hir::AssocItemConstraint<'tcx>>,
@@ -134,14 +134,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }) {
             return self.complain_about_assoc_kind_mismatch(
                 assoc_item,
-                assoc_kind,
+                assoc_tag,
                 assoc_ident,
                 span,
                 constraint,
             );
         }
 
-        let assoc_kind_str = assoc_kind_str(assoc_kind);
+        let assoc_kind_str = assoc_tag_str(assoc_tag);
         let qself_str = qself.to_string(tcx);
 
         // The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a
@@ -168,7 +168,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let all_candidate_names: Vec<_> = all_candidates()
             .flat_map(|r| tcx.associated_items(r.def_id()).in_definition_order())
             .filter_map(|item| {
-                (!item.is_impl_trait_in_trait() && item.kind == assoc_kind).then_some(item.name)
+                (!item.is_impl_trait_in_trait() && item.as_tag() == assoc_tag).then_some(item.name)
             })
             .collect();
 
@@ -200,7 +200,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .iter()
             .flat_map(|trait_def_id| tcx.associated_items(*trait_def_id).in_definition_order())
             .filter_map(|item| {
-                (!item.is_impl_trait_in_trait() && item.kind == assoc_kind).then_some(item.name)
+                (!item.is_impl_trait_in_trait() && item.as_tag() == assoc_tag).then_some(item.name)
             })
             .collect();
 
@@ -213,7 +213,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 .filter(|trait_def_id| {
                     tcx.associated_items(trait_def_id)
                         .filter_by_name_unhygienic(suggested_name)
-                        .any(|item| item.kind == assoc_kind)
+                        .any(|item| item.as_tag() == assoc_tag)
                 })
                 .collect::<Vec<_>>()[..]
             {
@@ -330,7 +330,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn complain_about_assoc_kind_mismatch(
         &self,
         assoc_item: &ty::AssocItem,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
         ident: Ident,
         span: Span,
         constraint: Option<&hir::AssocItemConstraint<'tcx>>,
@@ -375,17 +375,17 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 hir::Term::Ty(ty) => ty.span,
                 hir::Term::Const(ct) => ct.span(),
             };
-            (span, Some(ident.span), assoc_item.kind, assoc_kind)
+            (span, Some(ident.span), assoc_item.as_tag(), assoc_tag)
         } else {
-            (ident.span, None, assoc_kind, assoc_item.kind)
+            (ident.span, None, assoc_tag, assoc_item.as_tag())
         };
 
         self.dcx().emit_err(errors::AssocKindMismatch {
             span,
-            expected: assoc_kind_str(expected),
-            got: assoc_kind_str(got),
+            expected: assoc_tag_str(expected),
+            got: assoc_tag_str(got),
             expected_because_label,
-            assoc_kind: assoc_kind_str(assoc_item.kind),
+            assoc_kind: assoc_tag_str(assoc_item.as_tag()),
             def_span: tcx.def_span(assoc_item.def_id),
             bound_on_assoc_const_label,
             wrap_in_braces_sugg,
@@ -398,9 +398,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         types: &[String],
         traits: &[String],
         name: Symbol,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> ErrorGuaranteed {
-        let kind_str = assoc_kind_str(kind);
+        let kind_str = assoc_tag_str(assoc_tag);
         let mut err =
             struct_span_code_err!(self.dcx(), span, E0223, "ambiguous associated {kind_str}");
         if self
@@ -569,7 +569,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         candidates: Vec<(DefId, (DefId, DefId))>,
         fulfillment_errors: Vec<FulfillmentError<'tcx>>,
         span: Span,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> ErrorGuaranteed {
         // FIXME(fmease): This was copied in parts from an old version of `rustc_hir_typeck::method::suggest`.
         // Either
@@ -579,14 +579,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let tcx = self.tcx();
 
-        let kind_str = assoc_kind_str(kind);
+        let assoc_tag_str = assoc_tag_str(assoc_tag);
         let adt_did = self_ty.ty_adt_def().map(|def| def.did());
         let add_def_label = |err: &mut Diag<'_>| {
             if let Some(did) = adt_did {
                 err.span_label(
                     tcx.def_span(did),
                     format!(
-                        "associated {kind_str} `{name}` not found for this {}",
+                        "associated {assoc_tag_str} `{name}` not found for this {}",
                         tcx.def_descr(did)
                     ),
                 );
@@ -615,11 +615,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 self.dcx(),
                 name.span,
                 E0220,
-                "associated {kind_str} `{name}` not found for `{self_ty}` in the current scope"
+                "associated {assoc_tag_str} `{name}` not found for `{self_ty}` in the current scope"
             );
             err.span_label(name.span, format!("associated item not found in `{self_ty}`"));
             err.note(format!(
-                "the associated {kind_str} was found for\n{type_candidates}{additional_types}",
+                "the associated {assoc_tag_str} was found for\n{type_candidates}{additional_types}",
             ));
             add_def_label(&mut err);
             return err.emit();
@@ -700,7 +700,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let mut err = self.dcx().struct_span_err(
             name.span,
-            format!("the associated {kind_str} `{name}` exists for `{self_ty}`, but its trait bounds were not satisfied")
+            format!("the associated {assoc_tag_str} `{name}` exists for `{self_ty}`, but its trait bounds were not satisfied")
         );
         if !bounds.is_empty() {
             err.note(format!(
@@ -710,7 +710,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
         err.span_label(
             name.span,
-            format!("associated {kind_str} cannot be referenced on `{self_ty}` due to unsatisfied trait bounds")
+            format!("associated {assoc_tag_str} cannot be referenced on `{self_ty}` due to unsatisfied trait bounds")
         );
 
         for (span, mut bounds) in bound_spans {
@@ -812,7 +812,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     let assoc_item = tcx.associated_items(trait_def).find_by_ident_and_kind(
                         tcx,
                         ident,
-                        ty::AssocKind::Type,
+                        ty::AssocTag::Type,
                         trait_def,
                     );
 
@@ -1022,12 +1022,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         .map(|simple_ty| tcx.incoherent_impls(simple_ty))
                 })
             && let name = Symbol::intern(&format!("{ident2}_{ident3}"))
-            && let Some(ty::AssocItem { kind: ty::AssocKind::Fn, .. }) = inherent_impls
+            && let Some(item) = inherent_impls
                 .iter()
                 .flat_map(|inherent_impl| {
                     tcx.associated_items(inherent_impl).filter_by_name_unhygienic(name)
                 })
                 .next()
+            && item.is_fn()
         {
             Err(struct_span_code_err!(self.dcx(), span, E0223, "ambiguous associated type")
                 .with_span_suggestion_verbose(
@@ -1629,10 +1630,10 @@ fn generics_args_err_extend<'a>(
     }
 }
 
-pub(crate) fn assoc_kind_str(kind: ty::AssocKind) -> &'static str {
-    match kind {
-        ty::AssocKind::Fn => "function",
-        ty::AssocKind::Const => "constant",
-        ty::AssocKind::Type => "type",
+pub(crate) fn assoc_tag_str(assoc_tag: ty::AssocTag) -> &'static str {
+    match assoc_tag {
+        ty::AssocTag::Fn => "function",
+        ty::AssocTag::Const => "constant",
+        ty::AssocTag::Type => "type",
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 83aa0d9562015..0fb406d990803 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -38,8 +38,8 @@ use rustc_middle::middle::stability::AllowUnstable;
 use rustc_middle::mir::interpret::LitToConstInput;
 use rustc_middle::ty::print::PrintPolyTraitRefExt as _;
 use rustc_middle::ty::{
-    self, Const, GenericArgKind, GenericArgsRef, GenericParamDefKind, ParamEnv, Ty, TyCtxt,
-    TypeVisitableExt, TypingMode, Upcast, fold_regions,
+    self, AssocTag, Const, GenericArgKind, GenericArgsRef, GenericParamDefKind, ParamEnv, Ty,
+    TyCtxt, TypeVisitableExt, TypingMode, Upcast, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
@@ -51,7 +51,7 @@ use rustc_trait_selection::traits::wf::object_region_bounds;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 use tracing::{debug, instrument};
 
-use self::errors::assoc_kind_str;
+use self::errors::assoc_tag_str;
 use crate::check::check_abi_fn_ptr;
 use crate::errors::{AmbiguousLifetimeBound, BadReturnTypeNotation, NoVariantNamed};
 use crate::hir_ty_lowering::errors::{GenericsArgsErrExtend, prohibit_assoc_item_constraint};
@@ -168,7 +168,7 @@ pub trait HirTyLowerer<'tcx> {
         item_def_id: DefId,
         item_segment: &hir::PathSegment<'tcx>,
         poly_trait_ref: ty::PolyTraitRef<'tcx>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, GenericArgsRef<'tcx>), ErrorGuaranteed>;
 
     fn lower_fn_sig(
@@ -251,10 +251,10 @@ enum LowerAssocMode {
 }
 
 impl LowerAssocMode {
-    fn kind(self) -> ty::AssocKind {
+    fn assoc_tag(self) -> ty::AssocTag {
         match self {
-            LowerAssocMode::Type { .. } => ty::AssocKind::Type,
-            LowerAssocMode::Const => ty::AssocKind::Const,
+            LowerAssocMode::Type { .. } => ty::AssocTag::Type,
+            LowerAssocMode::Const => ty::AssocTag::Const,
         }
     }
 
@@ -268,7 +268,8 @@ impl LowerAssocMode {
     fn permit_variants(self) -> bool {
         match self {
             LowerAssocMode::Type { permit_variants } => permit_variants,
-            // FIXME(mgca): Support paths like `Option::<T>::None` or `Option::<T>::Some` which resolve to const ctors/fn items respectively
+            // FIXME(mgca): Support paths like `Option::<T>::None` or `Option::<T>::Some` which
+            // resolve to const ctors/fn items respectively.
             LowerAssocMode::Const => false,
         }
     }
@@ -932,12 +933,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn probe_trait_that_defines_assoc_item(
         &self,
         trait_def_id: DefId,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: AssocTag,
         assoc_ident: Ident,
     ) -> bool {
         self.tcx()
             .associated_items(trait_def_id)
-            .find_by_ident_and_kind(self.tcx(), assoc_ident, assoc_kind, trait_def_id)
+            .find_by_ident_and_kind(self.tcx(), assoc_ident, assoc_tag, trait_def_id)
             .is_some()
     }
 
@@ -975,7 +976,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         &self,
         ty_param_def_id: LocalDefId,
         ty_param_span: Span,
-        kind: ty::AssocKind,
+        assoc_tag: AssocTag,
         assoc_ident: Ident,
         span: Span,
     ) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed> {
@@ -993,7 +994,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 traits::transitive_bounds_that_define_assoc_item(tcx, trait_refs, assoc_ident)
             },
             AssocItemQSelf::TyParam(ty_param_def_id, ty_param_span),
-            kind,
+            assoc_tag,
             assoc_ident,
             span,
             None,
@@ -1010,7 +1011,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         &self,
         all_candidates: impl Fn() -> I,
         qself: AssocItemQSelf,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: AssocTag,
         assoc_ident: Ident,
         span: Span,
         constraint: Option<&hir::AssocItemConstraint<'tcx>>,
@@ -1021,14 +1022,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let tcx = self.tcx();
 
         let mut matching_candidates = all_candidates().filter(|r| {
-            self.probe_trait_that_defines_assoc_item(r.def_id(), assoc_kind, assoc_ident)
+            self.probe_trait_that_defines_assoc_item(r.def_id(), assoc_tag, assoc_ident)
         });
 
         let Some(bound) = matching_candidates.next() else {
             let reported = self.complain_about_assoc_item_not_found(
                 all_candidates,
                 qself,
-                assoc_kind,
+                assoc_tag,
                 assoc_ident,
                 span,
                 constraint,
@@ -1040,7 +1041,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         if let Some(bound2) = matching_candidates.next() {
             debug!(?bound2);
 
-            let assoc_kind_str = errors::assoc_kind_str(assoc_kind);
+            let assoc_kind_str = errors::assoc_tag_str(assoc_tag);
             let qself_str = qself.to_string(tcx);
             let mut err = self.dcx().create_err(crate::errors::AmbiguousAssocItem {
                 span,
@@ -1059,14 +1060,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 },
             );
 
-            // FIXME(#97583): Print associated item bindings properly (i.e., not as equality predicates!).
+            // FIXME(#97583): Print associated item bindings properly (i.e., not as equality
+            // predicates!).
             // FIXME: Turn this into a structured, translateable & more actionable suggestion.
             let mut where_bounds = vec![];
             for bound in [bound, bound2].into_iter().chain(matching_candidates) {
                 let bound_id = bound.def_id();
                 let bound_span = tcx
                     .associated_items(bound_id)
-                    .find_by_ident_and_kind(tcx, assoc_ident, assoc_kind, bound_id)
+                    .find_by_ident_and_kind(tcx, assoc_ident, assoc_tag, bound_id)
                     .and_then(|item| tcx.hir_span_if_local(item.def_id));
 
                 if let Some(bound_span) = bound_span {
@@ -1265,7 +1267,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 qself_ty,
                 hir_ref_id,
                 span,
-                mode.kind(),
+                mode.assoc_tag(),
             )? {
                 return Ok(LoweredAssoc::Term(did, args));
             }
@@ -1296,7 +1298,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         )
                     },
                     AssocItemQSelf::SelfTyAlias,
-                    mode.kind(),
+                    mode.assoc_tag(),
                     assoc_ident,
                     span,
                     None,
@@ -1308,12 +1310,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             ) => self.probe_single_ty_param_bound_for_assoc_item(
                 param_did.expect_local(),
                 qself.span,
-                mode.kind(),
+                mode.assoc_tag(),
                 assoc_ident,
                 span,
             )?,
             _ => {
-                let kind_str = assoc_kind_str(mode.kind());
+                let kind_str = assoc_tag_str(mode.assoc_tag());
                 let reported = if variant_resolution.is_some() {
                     // Variant in type position
                     let msg = format!("expected {kind_str}, found variant `{assoc_ident}`");
@@ -1420,7 +1422,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         &[qself_ty.to_string()],
                         &traits,
                         assoc_ident.name,
-                        mode.kind(),
+                        mode.assoc_tag(),
                     )
                 };
                 return Err(reported);
@@ -1429,10 +1431,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let trait_did = bound.def_id();
         let assoc_item = self
-            .probe_assoc_item(assoc_ident, mode.kind(), hir_ref_id, span, trait_did)
+            .probe_assoc_item(assoc_ident, mode.assoc_tag(), hir_ref_id, span, trait_did)
             .expect("failed to find associated item");
-        let (def_id, args) =
-            self.lower_assoc_shared(span, assoc_item.def_id, assoc_segment, bound, mode.kind())?;
+        let (def_id, args) = self.lower_assoc_shared(
+            span,
+            assoc_item.def_id,
+            assoc_segment,
+            bound,
+            mode.assoc_tag(),
+        )?;
         let result = LoweredAssoc::Term(def_id, args);
 
         if let Some(variant_def_id) = variant_resolution {
@@ -1469,20 +1476,21 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         self_ty: Ty<'tcx>,
         block: HirId,
         span: Span,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<Option<(DefId, GenericArgsRef<'tcx>)>, ErrorGuaranteed> {
         let tcx = self.tcx();
 
         if !tcx.features().inherent_associated_types() {
-            match kind {
-                // Don't attempt to look up inherent associated types when the feature is not enabled.
-                // Theoretically it'd be fine to do so since we feature-gate their definition site.
-                // However, due to current limitations of the implementation (caused by us performing
-                // selection during HIR ty lowering instead of in the trait solver), IATs can lead to cycle
-                // errors (#108491) which mask the feature-gate error, needlessly confusing users
-                // who use IATs by accident (#113265).
-                ty::AssocKind::Type => return Ok(None),
-                ty::AssocKind::Const => {
+            match assoc_tag {
+                // Don't attempt to look up inherent associated types when the feature is not
+                // enabled. Theoretically it'd be fine to do so since we feature-gate their
+                // definition site. However, due to current limitations of the implementation
+                // (caused by us performing selection during HIR ty lowering instead of in the
+                // trait solver), IATs can lead to cycle errors (#108491) which mask the
+                // feature-gate error, needlessly confusing users who use IATs by accident
+                // (#113265).
+                ty::AssocTag::Type => return Ok(None),
+                ty::AssocTag::Const => {
                     // We also gate the mgca codepath for type-level uses of inherent consts
                     // with the inherent_associated_types feature gate since it relies on the
                     // same machinery and has similar rough edges.
@@ -1494,7 +1502,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     )
                     .emit());
                 }
-                ty::AssocKind::Fn => unreachable!(),
+                ty::AssocTag::Fn => unreachable!(),
             }
         }
 
@@ -1503,7 +1511,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .inherent_impls(adt_did)
             .iter()
             .filter_map(|&impl_| {
-                let (item, scope) = self.probe_assoc_item_unchecked(name, kind, block, impl_)?;
+                let (item, scope) =
+                    self.probe_assoc_item_unchecked(name, assoc_tag, block, impl_)?;
                 Some((impl_, (item.def_id, scope)))
             })
             .collect();
@@ -1542,7 +1551,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             self_ty,
             |self_ty| {
                 self.select_inherent_assoc_candidates(
-                    infcx, name, span, self_ty, param_env, candidates, kind,
+                    infcx, name, span, self_ty, param_env, candidates, assoc_tag,
                 )
             },
         )?;
@@ -1570,7 +1579,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         self_ty: Ty<'tcx>,
         param_env: ParamEnv<'tcx>,
         candidates: Vec<(DefId, (DefId, DefId))>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, (DefId, DefId)), ErrorGuaranteed> {
         let tcx = self.tcx();
         let mut fulfillment_errors = Vec::new();
@@ -1621,7 +1630,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 candidates,
                 fulfillment_errors,
                 span,
-                kind,
+                assoc_tag,
             )),
 
             &[applicable_candidate] => Ok(applicable_candidate),
@@ -1640,12 +1649,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn probe_assoc_item(
         &self,
         ident: Ident,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
         block: HirId,
         span: Span,
         scope: DefId,
     ) -> Option<ty::AssocItem> {
-        let (item, scope) = self.probe_assoc_item_unchecked(ident, kind, block, scope)?;
+        let (item, scope) = self.probe_assoc_item_unchecked(ident, assoc_tag, block, scope)?;
         self.check_assoc_item(item.def_id, ident, scope, block, span);
         Some(item)
     }
@@ -1657,7 +1666,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn probe_assoc_item_unchecked(
         &self,
         ident: Ident,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
         block: HirId,
         scope: DefId,
     ) -> Option<(ty::AssocItem, /*scope*/ DefId)> {
@@ -1670,7 +1679,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let item = tcx
             .associated_items(scope)
             .filter_by_name_unhygienic(ident.name)
-            .find(|i| i.kind == kind && i.ident(tcx).normalize_to_macros_2_0() == ident)?;
+            .find(|i| i.as_tag() == assoc_tag && i.ident(tcx).normalize_to_macros_2_0() == ident)?;
 
         Some((*item, def_scope))
     }
@@ -1770,7 +1779,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             item_def_id,
             trait_segment,
             item_segment,
-            ty::AssocKind::Type,
+            ty::AssocTag::Type,
         ) {
             Ok((item_def_id, item_args)) => {
                 Ty::new_projection_from_args(self.tcx(), item_def_id, item_args)
@@ -1795,7 +1804,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             item_def_id,
             trait_segment,
             item_segment,
-            ty::AssocKind::Const,
+            ty::AssocTag::Const,
         ) {
             Ok((item_def_id, item_args)) => {
                 let uv = ty::UnevaluatedConst::new(item_def_id, item_args);
@@ -1813,7 +1822,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         item_def_id: DefId,
         trait_segment: &hir::PathSegment<'tcx>,
         item_segment: &hir::PathSegment<'tcx>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, GenericArgsRef<'tcx>), ErrorGuaranteed> {
         let tcx = self.tcx();
 
@@ -1821,7 +1830,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         debug!(?trait_def_id);
 
         let Some(self_ty) = opt_self_ty else {
-            return Err(self.error_missing_qpath_self_ty(trait_def_id, span, item_segment, kind));
+            return Err(self.error_missing_qpath_self_ty(
+                trait_def_id,
+                span,
+                item_segment,
+                assoc_tag,
+            ));
         };
         debug!(?self_ty);
 
@@ -1840,7 +1854,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         trait_def_id: DefId,
         span: Span,
         item_segment: &hir::PathSegment<'tcx>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> ErrorGuaranteed {
         let tcx = self.tcx();
         let path_str = tcx.def_path_str(trait_def_id);
@@ -1877,7 +1891,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // FIXME: also look at `tcx.generics_of(self.item_def_id()).params` any that
         // references the trait. Relevant for the first case in
         // `src/test/ui/associated-types/associated-types-in-ambiguous-context.rs`
-        self.report_ambiguous_assoc(span, &type_names, &[path_str], item_segment.ident.name, kind)
+        self.report_ambiguous_assoc(
+            span,
+            &type_names,
+            &[path_str],
+            item_segment.ident.name,
+            assoc_tag,
+        )
     }
 
     pub fn prohibit_generic_args<'a>(
@@ -2862,7 +2882,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let assoc = tcx.associated_items(trait_ref.def_id).find_by_ident_and_kind(
             tcx,
             *ident,
-            ty::AssocKind::Fn,
+            ty::AssocTag::Fn,
             trait_ref.def_id,
         )?;
 
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check.rs b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
index c30b39dfe7656..1ab36ce1dcb9e 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
@@ -119,7 +119,7 @@ pub(crate) fn enforce_impl_lifetime_params_are_constrained(
                         vec![]
                     }
                 }
-                ty::AssocKind::Fn | ty::AssocKind::Const => vec![],
+                ty::AssocKind::Fn { .. } | ty::AssocKind::Const => vec![],
             }
         })
         .collect();
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index fec459954107e..d1bc54ed73ead 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -1089,14 +1089,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     /// This function checks whether the method is not static and does not accept other parameters than `self`.
     fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
-        match method.kind {
-            ty::AssocKind::Fn => {
-                method.fn_has_self_parameter
-                    && self.tcx.fn_sig(method.def_id).skip_binder().inputs().skip_binder().len()
-                        == 1
-            }
-            _ => false,
-        }
+        method.is_method()
+            && self.tcx.fn_sig(method.def_id).skip_binder().inputs().skip_binder().len() == 1
     }
 
     /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index de2f039cb1c86..56c205b6f8794 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2588,9 +2588,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .into_iter()
                 .flat_map(|i| self.tcx.associated_items(i).in_definition_order())
                 // Only assoc fn with no receivers.
-                .filter(|item| {
-                    matches!(item.kind, ty::AssocKind::Fn) && !item.fn_has_self_parameter
-                })
+                .filter(|item| item.is_fn() && !item.is_method())
                 .filter_map(|item| {
                     // Only assoc fns that return `Self`
                     let fn_sig = self.tcx.fn_sig(item.def_id).skip_binder();
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 81eb8510785b5..3a0f3a4a5f0b7 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -616,7 +616,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if let Some((DefKind::AssocFn, def_id)) =
                     self.typeck_results.borrow().type_dependent_def(call_expr.hir_id)
                     && let Some(assoc) = tcx.opt_associated_item(def_id)
-                    && assoc.fn_has_self_parameter
+                    && assoc.is_method()
                 {
                     Some(*receiver)
                 } else {
@@ -642,8 +642,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     TraitsInScope,
                     |mut ctxt| ctxt.probe_for_similar_candidate(),
                 )
-                && let ty::AssocKind::Fn = assoc.kind
-                && assoc.fn_has_self_parameter
+                && assoc.is_method()
             {
                 let args = self.infcx.fresh_args_for_item(call_name.span, assoc.def_id);
                 let fn_sig = tcx.fn_sig(assoc.def_id).instantiate(tcx, args);
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
index e14f1528d2c4c..74cc8181418c5 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -314,7 +314,7 @@ impl<'tcx> HirTyLowerer<'tcx> for FnCtxt<'_, 'tcx> {
         item_def_id: DefId,
         item_segment: &rustc_hir::PathSegment<'tcx>,
         poly_trait_ref: ty::PolyTraitRef<'tcx>,
-        _kind: ty::AssocKind,
+        _assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, ty::GenericArgsRef<'tcx>), ErrorGuaranteed> {
         let trait_ref = self.instantiate_binder_with_fresh_vars(
             span,
diff --git a/compiler/rustc_hir_typeck/src/method/mod.rs b/compiler/rustc_hir_typeck/src/method/mod.rs
index ddfd27ccf6b7f..39cb139a199ed 100644
--- a/compiler/rustc_hir_typeck/src/method/mod.rs
+++ b/compiler/rustc_hir_typeck/src/method/mod.rs
@@ -379,7 +379,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         let def_id = method_item.def_id;
-        if method_item.kind != ty::AssocKind::Fn {
+        if !method_item.is_fn() {
             span_bug!(tcx.def_span(def_id), "expected `{m_name}` to be an associated function");
         }
 
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 0a01ec89a327d..d5d85c812b2db 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -992,7 +992,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
     fn matches_return_type(&self, method: ty::AssocItem, expected: Ty<'tcx>) -> bool {
         match method.kind {
-            ty::AssocKind::Fn => self.probe(|_| {
+            ty::AssocKind::Fn { .. } => self.probe(|_| {
                 let args = self.fresh_args_for_item(self.span, method.def_id);
                 let fty = self.tcx.fn_sig(method.def_id).instantiate(self.tcx, args);
                 let fty = self.instantiate_binder_with_fresh_vars(self.span, infer::FnCall, fty);
@@ -1678,7 +1678,6 @@ impl<'tcx> Pick<'tcx> {
                     kind: _,
                     container: _,
                     trait_item_def_id: _,
-                    fn_has_self_parameter: _,
                     opt_rpitit_info: _,
                 },
             kind: _,
@@ -1712,7 +1711,7 @@ impl<'tcx> Pick<'tcx> {
             ));
 
             match (self.item.kind, self.item.container) {
-                (ty::AssocKind::Fn, _) => {
+                (ty::AssocKind::Fn { .. }, _) => {
                     // FIXME: This should be a `span_suggestion` instead of `help`
                     // However `self.span` only
                     // highlights the method name, so we can't use it. Also consider reusing
@@ -2252,10 +2251,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         // In Path mode (i.e., resolving a value like `T::next`), consider any
         // associated value (i.e., methods, constants) but not types.
         match self.mode {
-            Mode::MethodCall => item.fn_has_self_parameter,
+            Mode::MethodCall => item.is_method(),
             Mode::Path => match item.kind {
                 ty::AssocKind::Type => false,
-                ty::AssocKind::Fn | ty::AssocKind::Const => true,
+                ty::AssocKind::Fn { .. } | ty::AssocKind::Const => true,
             },
         }
         // FIXME -- check for types that deref to `Self`,
@@ -2277,7 +2276,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         impl_ty: Ty<'tcx>,
         args: GenericArgsRef<'tcx>,
     ) -> (Ty<'tcx>, Option<Ty<'tcx>>) {
-        if item.kind == ty::AssocKind::Fn && self.mode == Mode::MethodCall {
+        if item.is_fn() && self.mode == Mode::MethodCall {
             let sig = self.xform_method_sig(item.def_id, args);
             (sig.inputs()[0], Some(sig.output()))
         } else {
@@ -2328,8 +2327,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     /// Determine if the given associated item type is relevant in the current context.
     fn is_relevant_kind_for_mode(&self, kind: ty::AssocKind) -> bool {
         match (self.mode, kind) {
-            (Mode::MethodCall, ty::AssocKind::Fn) => true,
-            (Mode::Path, ty::AssocKind::Const | ty::AssocKind::Fn) => true,
+            (Mode::MethodCall, ty::AssocKind::Fn { .. }) => true,
+            (Mode::Path, ty::AssocKind::Const | ty::AssocKind::Fn { .. }) => true,
             _ => false,
         }
     }
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 68f13d654d6e8..1b9771636a7d8 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -713,7 +713,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && let Some(candidate) = tcx.associated_items(impl_def_id).find_by_ident_and_kind(
                     self.tcx,
                     item_ident,
-                    ty::AssocKind::Type,
+                    ty::AssocTag::Type,
                     impl_def_id,
                 )
                 && let Some(adt_def) = tcx.type_of(candidate.def_id).skip_binder().ty_adt_def()
@@ -1442,7 +1442,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             if let Some(assoc) = self.associated_value(*def_id, item_ident) {
                                 // Check for both mode is the same so we avoid suggesting
                                 // incorrect associated item.
-                                match (mode, assoc.fn_has_self_parameter, source) {
+                                match (mode, assoc.is_method(), source) {
                                     (Mode::MethodCall, true, SelfSource::MethodCall(_)) => {
                                         // We check that the suggest type is actually
                                         // different from the received one
@@ -1834,7 +1834,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let ty_args = self.infcx.fresh_args_for_item(span, similar_candidate.def_id);
             let fn_sig = tcx.fn_sig(similar_candidate.def_id).instantiate(tcx, ty_args);
             let fn_sig = self.instantiate_binder_with_fresh_vars(span, infer::FnCall, fn_sig);
-            if similar_candidate.fn_has_self_parameter {
+            if similar_candidate.is_method() {
                 if let Some(args) = args
                     && fn_sig.inputs()[1..].len() == args.len()
                 {
@@ -1902,7 +1902,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 {
                     if let Some(candidates) = find_attr!(self.tcx.get_all_attrs(inherent_method.def_id), AttributeKind::Confusables{symbols, ..} => symbols)
                         && candidates.contains(&item_name.name)
-                        && let ty::AssocKind::Fn = inherent_method.kind
+                        && inherent_method.is_fn()
                     {
                         let args =
                             ty::GenericArgs::identity_for_item(self.tcx, inherent_method.def_id)
@@ -2116,8 +2116,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Only assoc fn with no receivers and only if
             // they are resolvable
             .filter(|item| {
-                matches!(item.kind, ty::AssocKind::Fn)
-                    && !item.fn_has_self_parameter
+                matches!(item.kind, ty::AssocKind::Fn { has_self: false })
                     && self
                         .probe_for_name(
                             Mode::Path,
@@ -2261,7 +2260,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 };
 
                 let assoc = self.associated_value(assoc_did, item_name)?;
-                if assoc.kind != ty::AssocKind::Fn {
+                if !assoc.is_fn() {
                     return None;
                 }
 
@@ -3208,7 +3207,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // If this method receives `&self`, then the provided
                     // argument _should_ coerce, so it's valid to suggest
                     // just changing the path.
-                    && pick.item.fn_has_self_parameter
+                    && pick.item.is_method()
                     && let Some(self_ty) =
                         self.tcx.fn_sig(pick.item.def_id).instantiate_identity().inputs().skip_binder().get(0)
                     && self_ty.is_ref()
@@ -3560,7 +3559,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             || (("Pin::new" == *pre)
                                 && ((sym::as_ref == item_name.name) || !unpin))
                             || inputs_len.is_some_and(|inputs_len| {
-                                pick.item.kind == ty::AssocKind::Fn
+                                pick.item.is_fn()
                                     && self
                                         .tcx
                                         .fn_sig(pick.item.def_id)
@@ -3618,7 +3617,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     && pick.autoderefs == 0
                     // Check that the method of the same name that was found on the new `Pin<T>`
                     // receiver has the same number of arguments that appear in the user's code.
-                    && inputs_len.is_some_and(|inputs_len| pick.item.kind == ty::AssocKind::Fn && self.tcx.fn_sig(pick.item.def_id).skip_binder().skip_binder().inputs().len() == inputs_len)
+                    && inputs_len.is_some_and(|inputs_len| pick.item.is_fn() && self.tcx.fn_sig(pick.item.def_id).skip_binder().skip_binder().inputs().len() == inputs_len)
                 {
                     let indent = self
                         .tcx
@@ -3756,7 +3755,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     && self
                         .associated_value(info.def_id, item_name)
                         .filter(|item| {
-                            if let ty::AssocKind::Fn = item.kind {
+                            if item.is_fn() {
                                 let id = item
                                     .def_id
                                     .as_local()
@@ -4279,13 +4278,13 @@ fn print_disambiguation_help<'tcx>(
     item: ty::AssocItem,
 ) -> Option<String> {
     let trait_impl_type = trait_ref.self_ty().peel_refs();
-    let trait_ref = if item.fn_has_self_parameter {
+    let trait_ref = if item.is_method() {
         trait_ref.print_only_trait_name().to_string()
     } else {
         format!("<{} as {}>", trait_ref.args[0], trait_ref.print_only_trait_name())
     };
     Some(
-        if matches!(item.kind, ty::AssocKind::Fn)
+        if item.is_fn()
             && let SelfSource::MethodCall(receiver) = source
             && let Some(args) = args
         {
@@ -4304,7 +4303,7 @@ fn print_disambiguation_help<'tcx>(
             let args = if let Some(first_arg_type) = first_arg_type
                 && (first_arg_type == tcx.types.self_param
                     || first_arg_type == trait_impl_type
-                    || item.fn_has_self_parameter)
+                    || item.is_method())
             {
                 Some(receiver)
             } else {
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index a2d5ffe256d5c..dd3c514704a1a 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -859,12 +859,7 @@ impl<'tcx> LateContext<'tcx> {
     ) -> Option<Ty<'tcx>> {
         let tcx = self.tcx;
         tcx.associated_items(trait_id)
-            .find_by_ident_and_kind(
-                tcx,
-                Ident::with_dummy_span(name),
-                ty::AssocKind::Type,
-                trait_id,
-            )
+            .find_by_ident_and_kind(tcx, Ident::with_dummy_span(name), ty::AssocTag::Type, trait_id)
             .and_then(|assoc| {
                 let proj = Ty::new_projection(tcx, assoc.def_id, [self_ty]);
                 tcx.try_normalize_erasing_regions(self.typing_env(), proj).ok()
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 4cc12ca2e0bfd..cc3b2a241e4ad 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1337,10 +1337,12 @@ impl<'a> CrateMetadataRef<'a> {
         } else {
             self.item_name(id)
         };
-        let (kind, has_self) = match self.def_kind(id) {
-            DefKind::AssocConst => (ty::AssocKind::Const, false),
-            DefKind::AssocFn => (ty::AssocKind::Fn, self.get_fn_has_self_parameter(id, sess)),
-            DefKind::AssocTy => (ty::AssocKind::Type, false),
+        let kind = match self.def_kind(id) {
+            DefKind::AssocConst => ty::AssocKind::Const,
+            DefKind::AssocFn => {
+                ty::AssocKind::Fn { has_self: self.get_fn_has_self_parameter(id, sess) }
+            }
+            DefKind::AssocTy => ty::AssocKind::Type,
             _ => bug!("cannot get associated-item of `{:?}`", self.def_key(id)),
         };
         let container = self.root.tables.assoc_container.get(self, id).unwrap();
@@ -1353,7 +1355,6 @@ impl<'a> CrateMetadataRef<'a> {
             def_id: self.local_def_id(id),
             trait_item_def_id: self.get_trait_item_def_id(id),
             container,
-            fn_has_self_parameter: has_self,
             opt_rpitit_info,
         }
     }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 5c8e2888ec984..cc9da16ffdbb0 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1338,7 +1338,7 @@ fn should_encode_const(def_kind: DefKind) -> bool {
 fn should_encode_fn_impl_trait_in_trait<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
     if let Some(assoc_item) = tcx.opt_associated_item(def_id)
         && assoc_item.container == ty::AssocItemContainer::Trait
-        && assoc_item.kind == ty::AssocKind::Fn
+        && assoc_item.is_fn()
     {
         true
     } else {
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 4dfb362f3a22b..db19c858e7c18 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -1636,8 +1636,8 @@ pub fn find_self_call<'tcx>(
         &body[block].terminator
         && let Operand::Constant(box ConstOperand { const_, .. }) = func
         && let ty::FnDef(def_id, fn_args) = *const_.ty().kind()
-        && let Some(ty::AssocItem { fn_has_self_parameter: true, .. }) =
-            tcx.opt_associated_item(def_id)
+        && let Some(item) = tcx.opt_associated_item(def_id)
+        && item.is_method()
         && let [Spanned { node: Operand::Move(self_place) | Operand::Copy(self_place), .. }, ..] =
             **args
     {
diff --git a/compiler/rustc_middle/src/ty/adjustment.rs b/compiler/rustc_middle/src/ty/adjustment.rs
index f8ab555305f05..3425da4855950 100644
--- a/compiler/rustc_middle/src/ty/adjustment.rs
+++ b/compiler/rustc_middle/src/ty/adjustment.rs
@@ -5,7 +5,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_span::Span;
 
-use crate::ty::{self, Ty, TyCtxt};
+use crate::ty::{Ty, TyCtxt};
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
 pub enum PointerCoercion {
@@ -133,7 +133,7 @@ impl OverloadedDeref {
         };
         tcx.associated_items(trait_def_id)
             .in_definition_order()
-            .find(|m| m.kind == ty::AssocKind::Fn)
+            .find(|item| item.is_fn())
             .unwrap()
             .def_id
     }
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index bbaf735fbdb94..3c1e5ed9e114d 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -26,10 +26,6 @@ pub struct AssocItem {
     /// the associated item on the trait that this implements.
     pub trait_item_def_id: Option<DefId>,
 
-    /// Whether this is a method with an explicit self
-    /// as its first parameter, allowing method calls.
-    pub fn_has_self_parameter: bool,
-
     /// `Some` if the associated item (an associated type) comes from the
     /// return-position `impl Trait` in trait desugaring. The `ImplTraitInTraitData`
     /// provides additional information about its source.
@@ -78,7 +74,7 @@ impl AssocItem {
 
     pub fn signature(&self, tcx: TyCtxt<'_>) -> String {
         match self.kind {
-            ty::AssocKind::Fn => {
+            ty::AssocKind::Fn { .. } => {
                 // We skip the binder here because the binder would deanonymize all
                 // late-bound regions, and we don't want method signatures to show up
                 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
@@ -99,12 +95,28 @@ impl AssocItem {
     pub fn descr(&self) -> &'static str {
         match self.kind {
             ty::AssocKind::Const => "associated const",
-            ty::AssocKind::Fn if self.fn_has_self_parameter => "method",
-            ty::AssocKind::Fn => "associated function",
+            ty::AssocKind::Fn { has_self: true } => "method",
+            ty::AssocKind::Fn { has_self: false } => "associated function",
             ty::AssocKind::Type => "associated type",
         }
     }
 
+    pub fn is_fn(&self) -> bool {
+        matches!(self.kind, ty::AssocKind::Fn { .. })
+    }
+
+    pub fn is_method(&self) -> bool {
+        matches!(self.kind, ty::AssocKind::Fn { has_self: true })
+    }
+
+    pub fn as_tag(&self) -> AssocTag {
+        match self.kind {
+            AssocKind::Const => AssocTag::Const,
+            AssocKind::Fn { .. } => AssocTag::Fn,
+            AssocKind::Type => AssocTag::Type,
+        }
+    }
+
     pub fn is_impl_trait_in_trait(&self) -> bool {
         self.opt_rpitit_info.is_some()
     }
@@ -131,7 +143,7 @@ impl AssocItem {
 #[derive(Copy, Clone, PartialEq, Debug, HashStable, Eq, Hash, Encodable, Decodable)]
 pub enum AssocKind {
     Const,
-    Fn,
+    Fn { has_self: bool },
     Type,
 }
 
@@ -139,14 +151,14 @@ impl AssocKind {
     pub fn namespace(&self) -> Namespace {
         match *self {
             ty::AssocKind::Type => Namespace::TypeNS,
-            ty::AssocKind::Const | ty::AssocKind::Fn => Namespace::ValueNS,
+            ty::AssocKind::Const | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
         }
     }
 
     pub fn as_def_kind(&self) -> DefKind {
         match self {
             AssocKind::Const => DefKind::AssocConst,
-            AssocKind::Fn => DefKind::AssocFn,
+            AssocKind::Fn { .. } => DefKind::AssocFn,
             AssocKind::Type => DefKind::AssocTy,
         }
     }
@@ -155,15 +167,22 @@ impl AssocKind {
 impl std::fmt::Display for AssocKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            // FIXME: fails to distinguish between "associated function" and
-            // "method" because `has_self` isn't known here.
-            AssocKind::Fn => write!(f, "method"),
+            AssocKind::Fn { has_self: true } => write!(f, "method"),
+            AssocKind::Fn { has_self: false } => write!(f, "associated function"),
             AssocKind::Const => write!(f, "associated const"),
             AssocKind::Type => write!(f, "associated type"),
         }
     }
 }
 
+// Like `AssocKind`, but just the tag, no fields. Used in various kinds of matching.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum AssocTag {
+    Const,
+    Fn,
+    Type,
+}
+
 /// A list of `ty::AssocItem`s in definition order that allows for efficient lookup by name.
 ///
 /// When doing lookup by name, we try to postpone hygienic comparison for as long as possible since
@@ -207,27 +226,14 @@ impl AssocItems {
         &self,
         tcx: TyCtxt<'_>,
         ident: Ident,
-        kind: AssocKind,
+        assoc_tag: AssocTag,
         parent_def_id: DefId,
     ) -> Option<&ty::AssocItem> {
         self.filter_by_name_unhygienic(ident.name)
-            .filter(|item| item.kind == kind)
+            .filter(|item| item.as_tag() == assoc_tag)
             .find(|item| tcx.hygienic_eq(ident, item.ident(tcx), parent_def_id))
     }
 
-    /// Returns the associated item with the given identifier and any of `AssocKind`, if one
-    /// exists. The identifier is matched hygienically.
-    pub fn find_by_ident_and_kinds(
-        &self,
-        tcx: TyCtxt<'_>,
-        ident: Ident,
-        // Sorted in order of what kinds to look at
-        kinds: &[AssocKind],
-        parent_def_id: DefId,
-    ) -> Option<&ty::AssocItem> {
-        kinds.iter().find_map(|kind| self.find_by_ident_and_kind(tcx, ident, *kind, parent_def_id))
-    }
-
     /// Returns the associated item with the given identifier in the given `Namespace`, if one
     /// exists. The identifier is matched hygienically.
     pub fn find_by_ident_and_namespace(
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 07f2a602f2bf2..faad0a82acbf8 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -746,7 +746,7 @@ impl<'tcx> Instance<'tcx> {
         let call_once = tcx
             .associated_items(fn_once)
             .in_definition_order()
-            .find(|it| it.kind == ty::AssocKind::Fn)
+            .find(|it| it.is_fn())
             .unwrap()
             .def_id;
         let track_caller =
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index a2b3acac3f26b..30c889c39d938 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -1464,7 +1464,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
         self.associated_items(id)
             .in_definition_order()
-            .filter(move |item| item.kind == AssocKind::Fn && item.defaultness(self).has_value())
+            .filter(move |item| item.is_fn() && item.defaultness(self).has_value())
     }
 
     pub fn repr_options_of_def(self, did: LocalDefId) -> ReprOptions {
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 857b462b9eb1e..dfc11de283d80 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -819,7 +819,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Get an English description for the item's kind.
     pub fn def_kind_descr(self, def_kind: DefKind, def_id: DefId) -> &'static str {
         match def_kind {
-            DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "method",
+            DefKind::AssocFn if self.associated_item(def_id).is_method() => "method",
             DefKind::Closure if let Some(coroutine_kind) = self.coroutine_kind(def_id) => {
                 match coroutine_kind {
                     hir::CoroutineKind::Desugared(
@@ -873,7 +873,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Gets an English article for the [`TyCtxt::def_kind_descr`].
     pub fn def_kind_descr_article(self, def_kind: DefKind, def_id: DefId) -> &'static str {
         match def_kind {
-            DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "a",
+            DefKind::AssocFn if self.associated_item(def_id).is_method() => "a",
             DefKind::Closure if let Some(coroutine_kind) = self.coroutine_kind(def_id) => {
                 match coroutine_kind {
                     hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, ..) => "an",
diff --git a/compiler/rustc_mir_build/src/builder/matches/test.rs b/compiler/rustc_mir_build/src/builder/matches/test.rs
index d1f9d4c34fe1e..16da609299845 100644
--- a/compiler/rustc_mir_build/src/builder/matches/test.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/test.rs
@@ -715,7 +715,7 @@ fn trait_method<'tcx>(
     let item = tcx
         .associated_items(trait_def_id)
         .filter_by_name_unhygienic(method_name)
-        .find(|item| item.kind == ty::AssocKind::Fn)
+        .find(|item| item.is_fn())
         .expect("trait method not found");
 
     let method_ty = Ty::new_fn_def(tcx, item.def_id, args);
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index c9771467e499c..c13ffae364983 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -66,7 +66,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceKind<'tcx>) -> Body<
             let call_mut = tcx
                 .associated_items(fn_mut)
                 .in_definition_order()
-                .find(|it| it.kind == ty::AssocKind::Fn)
+                .find(|it| it.is_fn())
                 .unwrap()
                 .def_id;
 
diff --git a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
index 55d52d5075dcc..7251ef478c6f1 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
@@ -3,7 +3,7 @@ use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir::def_id::DefId;
 use rustc_middle::mir::visit::Visitor as MirVisitor;
 use rustc_middle::mir::{self, Location, traversal};
-use rustc_middle::ty::{self, AssocKind, Instance, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, AssocTag, Instance, Ty, TyCtxt, TypeFoldable};
 use rustc_session::Limit;
 use rustc_session::lint::builtin::LARGE_ASSIGNMENTS;
 use rustc_span::source_map::Spanned;
@@ -194,7 +194,7 @@ fn assoc_fn_of_type<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, fn_ident: Ident) ->
         if let Some(new) = tcx.associated_items(impl_def_id).find_by_ident_and_kind(
             tcx,
             fn_ident,
-            AssocKind::Fn,
+            AssocTag::Fn,
             def_id,
         ) {
             return Some(new.def_id);
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index c2761bd2717f4..ae81021e0bea1 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1994,7 +1994,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             .iter()
             .flat_map(|i| self.r.tcx.associated_items(i).in_definition_order())
             // Only assoc fn with no receivers.
-            .filter(|item| matches!(item.kind, ty::AssocKind::Fn) && !item.fn_has_self_parameter)
+            .filter(|item| item.is_fn() && !item.is_method())
             .filter_map(|item| {
                 // Only assoc fns that return `Self`
                 let fn_sig = self.r.tcx.fn_sig(item.def_id).skip_binder();
diff --git a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
index 129a32c6edd81..718b9a4fa3b81 100644
--- a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
+++ b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
@@ -446,7 +446,7 @@ pub(crate) fn transform_instance<'tcx>(
             let call = tcx
                 .associated_items(trait_id)
                 .in_definition_order()
-                .find(|it| it.kind == ty::AssocKind::Fn)
+                .find(|it| it.is_fn())
                 .expect("No call-family function on closure-like Fn trait?")
                 .def_id;
 
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
index 28fc68d5e491b..94f3be9fef734 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
@@ -896,9 +896,9 @@ impl<'tcx> Stable<'tcx> for ty::AssocKind {
 
     fn stable(&self, _tables: &mut Tables<'_>) -> Self::T {
         use stable_mir::ty::AssocKind;
-        match self {
+        match *self {
             ty::AssocKind::Const => AssocKind::Const,
-            ty::AssocKind::Fn => AssocKind::Fn,
+            ty::AssocKind::Fn { has_self } => AssocKind::Fn { has_self },
             ty::AssocKind::Type => AssocKind::Type,
         }
     }
@@ -926,7 +926,6 @@ impl<'tcx> Stable<'tcx> for ty::AssocItem {
             kind: self.kind.stable(tables),
             container: self.container.stable(tables),
             trait_item_def_id: self.trait_item_def_id.map(|did| tables.assoc_def(did)),
-            fn_has_self_parameter: self.fn_has_self_parameter,
             opt_rpitit_info: self.opt_rpitit_info.map(|rpitit| rpitit.stable(tables)),
         }
     }
diff --git a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
index 439ebe978e591..60d9e122940bf 100644
--- a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
+++ b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
@@ -22,7 +22,8 @@ impl Display for Ty {
 impl Display for AssocKind {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self {
-            AssocKind::Fn => write!(f, "method"),
+            AssocKind::Fn { has_self: true } => write!(f, "method"),
+            AssocKind::Fn { has_self: false } => write!(f, "associated function"),
             AssocKind::Const => write!(f, "associated const"),
             AssocKind::Type => write!(f, "associated type"),
         }
diff --git a/compiler/rustc_smir/src/stable_mir/ty.rs b/compiler/rustc_smir/src/stable_mir/ty.rs
index 3fcbbb0e138be..63ce756162a52 100644
--- a/compiler/rustc_smir/src/stable_mir/ty.rs
+++ b/compiler/rustc_smir/src/stable_mir/ty.rs
@@ -1586,10 +1586,6 @@ pub struct AssocItem {
     /// the associated item on the trait that this implements.
     pub trait_item_def_id: Option<AssocDef>,
 
-    /// Whether this is a method with an explicit self
-    /// as its first parameter, allowing method calls.
-    pub fn_has_self_parameter: bool,
-
     /// `Some` if the associated item (an associated type) comes from the
     /// return-position `impl Trait` in trait desugaring. The `ImplTraitInTraitData`
     /// provides additional information about its source.
@@ -1599,7 +1595,7 @@ pub struct AssocItem {
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 pub enum AssocKind {
     Const,
-    Fn,
+    Fn { has_self: bool },
     Type,
 }
 
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
index 40f8af1f6913a..cbadb46c17d94 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -2334,7 +2334,7 @@ impl<'tcx> ObligationCause<'tcx> {
         subdiags: Vec<TypeErrorAdditionalDiags>,
     ) -> ObligationCauseFailureCode {
         match self.code() {
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 ObligationCauseFailureCode::MethodCompat { span, subdiags }
             }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
@@ -2398,7 +2398,7 @@ impl<'tcx> ObligationCause<'tcx> {
 
     fn as_requirement_str(&self) -> &'static str {
         match self.code() {
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 "method type is compatible with trait"
             }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
@@ -2422,7 +2422,9 @@ pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
 impl IntoDiagArg for ObligationCauseAsDiagArg<'_> {
     fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> rustc_errors::DiagArgValue {
         let kind = match self.0.code() {
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => "method_compat",
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
+                "method_compat"
+            }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => "type_compat",
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
                 "const_compat"
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
index 742059228510d..b66bd2c6ab787 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
@@ -98,7 +98,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let assoc_item = self.tcx().associated_item(trait_item_def_id);
         let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] };
         match assoc_item.kind {
-            ty::AssocKind::Fn => {
+            ty::AssocKind::Fn { .. } => {
                 if let Some(hir_id) =
                     assoc_item.def_id.as_local().map(|id| self.tcx().local_def_id_to_hir_id(id))
                 {
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
index fd2d2fa721054..4a71ab4e06a35 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
@@ -158,6 +158,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             && self
                 .tcx()
                 .opt_associated_item(scope_def_id.to_def_id())
-                .is_some_and(|i| i.fn_has_self_parameter)
+                .is_some_and(|i| i.is_method())
     }
 }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
index 5583deda99a49..02f21b5465c64 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
@@ -782,7 +782,7 @@ fn foo(&self) -> Self::T { String::new() }
         let methods: Vec<(Span, String)> = items
             .in_definition_order()
             .filter(|item| {
-                ty::AssocKind::Fn == item.kind
+                item.is_fn()
                     && Some(item.name) != current_method_ident
                     && !tcx.is_doc_hidden(item.def_id)
             })
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
index 59c93db9c8fff..e3e1583a48fac 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
@@ -349,7 +349,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     {
                         let (verb, noun) = match self.tcx.associated_item(item_id).kind {
                             ty::AssocKind::Const => ("refer to the", "constant"),
-                            ty::AssocKind::Fn => ("call", "function"),
+                            ty::AssocKind::Fn { .. } => ("call", "function"),
                             // This is already covered by E0223, but this following single match
                             // arm doesn't hurt here.
                             ty::AssocKind::Type => ("refer to the", "type"),
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index b963e4a2c7c4d..38aac8e70b529 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -5411,7 +5411,7 @@ fn point_at_assoc_type_restriction<G: EmissionGuarantee>(
                 tcx.associated_items(data.impl_or_alias_def_id).find_by_ident_and_kind(
                     tcx,
                     Ident::with_dummy_span(name),
-                    ty::AssocKind::Type,
+                    ty::AssocTag::Type,
                     data.impl_or_alias_def_id,
                 )
             {
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index bf9fcb0915a56..76892db9ef7b4 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -301,7 +301,7 @@ pub fn dyn_compatibility_violations_for_assoc_item(
         ty::AssocKind::Const => {
             vec![DynCompatibilityViolation::AssocConst(item.name, item.ident(tcx).span)]
         }
-        ty::AssocKind::Fn => virtual_call_violations_for_method(tcx, trait_def_id, item)
+        ty::AssocKind::Fn { .. } => virtual_call_violations_for_method(tcx, trait_def_id, item)
             .into_iter()
             .map(|v| {
                 let node = tcx.hir_get_if_local(item.def_id);
@@ -344,7 +344,7 @@ fn virtual_call_violations_for_method<'tcx>(
     let sig = tcx.fn_sig(method.def_id).instantiate_identity();
 
     // The method's first parameter must be named `self`
-    if !method.fn_has_self_parameter {
+    if !method.is_method() {
         let sugg = if let Some(hir::Node::TraitItem(hir::TraitItem {
             generics,
             kind: hir::TraitItemKind::Fn(sig, _),
diff --git a/compiler/rustc_trait_selection/src/traits/vtable.rs b/compiler/rustc_trait_selection/src/traits/vtable.rs
index 165174c0bcc15..3565c11249ad1 100644
--- a/compiler/rustc_trait_selection/src/traits/vtable.rs
+++ b/compiler/rustc_trait_selection/src/traits/vtable.rs
@@ -197,10 +197,8 @@ fn own_existential_vtable_entries_iter(
     tcx: TyCtxt<'_>,
     trait_def_id: DefId,
 ) -> impl Iterator<Item = DefId> {
-    let trait_methods = tcx
-        .associated_items(trait_def_id)
-        .in_definition_order()
-        .filter(|item| item.kind == ty::AssocKind::Fn);
+    let trait_methods =
+        tcx.associated_items(trait_def_id).in_definition_order().filter(|item| item.is_fn());
 
     // Now list each method's DefId (for within its trait).
     let own_entries = trait_methods.filter_map(move |&trait_method| {
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index 9520d948f51f3..79de071b6878e 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -129,10 +129,10 @@ fn associated_item(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::AssocItem {
 
 fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty::AssocItem {
     let owner_id = trait_item_ref.id.owner_id;
-    let (kind, has_self) = match trait_item_ref.kind {
-        hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
-        hir::AssocItemKind::Fn { has_self } => (ty::AssocKind::Fn, has_self),
-        hir::AssocItemKind::Type => (ty::AssocKind::Type, false),
+    let kind = match trait_item_ref.kind {
+        hir::AssocItemKind::Const => ty::AssocKind::Const,
+        hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { has_self },
+        hir::AssocItemKind::Type => ty::AssocKind::Type,
     };
 
     ty::AssocItem {
@@ -141,17 +141,16 @@ fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty
         def_id: owner_id.to_def_id(),
         trait_item_def_id: Some(owner_id.to_def_id()),
         container: ty::AssocItemContainer::Trait,
-        fn_has_self_parameter: has_self,
         opt_rpitit_info: None,
     }
 }
 
 fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::AssocItem {
     let def_id = impl_item_ref.id.owner_id;
-    let (kind, has_self) = match impl_item_ref.kind {
-        hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
-        hir::AssocItemKind::Fn { has_self } => (ty::AssocKind::Fn, has_self),
-        hir::AssocItemKind::Type => (ty::AssocKind::Type, false),
+    let kind = match impl_item_ref.kind {
+        hir::AssocItemKind::Const => ty::AssocKind::Const,
+        hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { has_self },
+        hir::AssocItemKind::Type => ty::AssocKind::Type,
     };
 
     ty::AssocItem {
@@ -160,7 +159,6 @@ fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::A
         def_id: def_id.to_def_id(),
         trait_item_def_id: impl_item_ref.trait_item_def_id,
         container: ty::AssocItemContainer::Impl,
-        fn_has_self_parameter: has_self,
         opt_rpitit_info: None,
     }
 }
@@ -269,7 +267,6 @@ fn associated_type_for_impl_trait_in_trait(
         def_id,
         trait_item_def_id: None,
         container: ty::AssocItemContainer::Trait,
-        fn_has_self_parameter: false,
         opt_rpitit_info: Some(ImplTraitInTraitData::Trait {
             fn_def_id: fn_def_id.to_def_id(),
             opaque_def_id: opaque_ty_def_id.to_def_id(),
@@ -322,7 +319,6 @@ fn associated_type_for_impl_trait_in_impl(
         def_id,
         trait_item_def_id: Some(trait_assoc_def_id),
         container: ty::AssocItemContainer::Impl,
-        fn_has_self_parameter: false,
         opt_rpitit_info: Some(ImplTraitInTraitData::Impl { fn_def_id: impl_fn_def_id.to_def_id() }),
     });
 
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 3a2b6974681bc..2f6870e3c368f 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -490,17 +490,17 @@ pub(crate) fn build_impl(
                         return true;
                     }
                     if let Some(associated_trait) = associated_trait {
-                        let assoc_kind = match item.kind {
-                            hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
-                            hir::ImplItemKind::Fn(..) => ty::AssocKind::Fn,
-                            hir::ImplItemKind::Type(..) => ty::AssocKind::Type,
+                        let assoc_tag = match item.kind {
+                            hir::ImplItemKind::Const(..) => ty::AssocTag::Const,
+                            hir::ImplItemKind::Fn(..) => ty::AssocTag::Fn,
+                            hir::ImplItemKind::Type(..) => ty::AssocTag::Type,
                         };
                         let trait_item = tcx
                             .associated_items(associated_trait.def_id)
                             .find_by_ident_and_kind(
                                 tcx,
                                 item.ident,
-                                assoc_kind,
+                                assoc_tag,
                                 associated_trait.def_id,
                             )
                             .unwrap(); // SAFETY: For all impl items there exists trait item that has the same name.
@@ -527,7 +527,7 @@ pub(crate) fn build_impl(
                             .find_by_ident_and_kind(
                                 tcx,
                                 item.ident(tcx),
-                                item.kind,
+                                item.as_tag(),
                                 associated_trait.def_id,
                             )
                             .unwrap(); // corresponding associated item has to exist
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 45a915719e9f2..7cfd204aa1375 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1374,10 +1374,10 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
                 }
             }
         }
-        ty::AssocKind::Fn => {
+        ty::AssocKind::Fn { has_self } => {
             let mut item = inline::build_function(cx, assoc_item.def_id);
 
-            if assoc_item.fn_has_self_parameter {
+            if has_self {
                 let self_ty = match assoc_item.container {
                     ty::AssocItemContainer::Impl => {
                         tcx.type_of(assoc_item.container_id(tcx)).instantiate_identity()
diff --git a/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs b/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
index ad18c7039eedf..4a876b854165e 100644
--- a/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
+++ b/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
@@ -56,7 +56,7 @@ fn is_impl_not_trait_with_bool_out<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -
             cx.tcx.associated_items(trait_id).find_by_ident_and_kind(
                 cx.tcx,
                 Ident::from_str("Output"),
-                ty::AssocKind::Type,
+                ty::AssocTag::Type,
                 trait_id,
             )
         })
diff --git a/src/tools/clippy/clippy_lints/src/len_zero.rs b/src/tools/clippy/clippy_lints/src/len_zero.rs
index b01929747d69c..77085d52a32ed 100644
--- a/src/tools/clippy/clippy_lints/src/len_zero.rs
+++ b/src/tools/clippy/clippy_lints/src/len_zero.rs
@@ -13,7 +13,7 @@ use rustc_hir::{
     QPath, TraitItemRef, TyKind,
 };
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::{self, AssocKind, FnSig, Ty};
+use rustc_middle::ty::{self, FnSig, Ty};
 use rustc_session::declare_lint_pass;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::sym;
@@ -288,8 +288,7 @@ fn check_trait_items(cx: &LateContext<'_>, visited_trait: &Item<'_>, ident: Iden
             .items()
             .flat_map(|&i| cx.tcx.associated_items(i).filter_by_name_unhygienic(is_empty))
             .any(|i| {
-                i.kind == AssocKind::Fn
-                    && i.fn_has_self_parameter
+                i.is_method()
                     && cx.tcx.fn_sig(i.def_id).skip_binder().inputs().skip_binder().len() == 1
             });
 
@@ -466,7 +465,7 @@ fn check_for_is_empty(
         .inherent_impls(impl_ty)
         .iter()
         .flat_map(|&id| cx.tcx.associated_items(id).filter_by_name_unhygienic(is_empty))
-        .find(|item| item.kind == AssocKind::Fn);
+        .find(|item| item.is_fn());
 
     let (msg, is_empty_span, self_kind) = match is_empty {
         None => (
@@ -486,7 +485,7 @@ fn check_for_is_empty(
             None,
         ),
         Some(is_empty)
-            if !(is_empty.fn_has_self_parameter
+            if !(is_empty.is_method()
                 && check_is_empty_sig(
                     cx,
                     cx.tcx.fn_sig(is_empty.def_id).instantiate_identity().skip_binder(),
@@ -608,7 +607,7 @@ fn is_empty_array(expr: &Expr<'_>) -> bool {
 fn has_is_empty(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     /// Gets an `AssocItem` and return true if it matches `is_empty(self)`.
     fn is_is_empty(cx: &LateContext<'_>, item: &ty::AssocItem) -> bool {
-        if item.kind == AssocKind::Fn {
+        if item.is_fn() {
             let sig = cx.tcx.fn_sig(item.def_id).skip_binder();
             let ty = sig.skip_binder();
             ty.inputs().len() == 1
diff --git a/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs b/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
index 239ee6c729fb0..e4a29b6560e52 100644
--- a/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
@@ -17,7 +17,7 @@ use rustc_hir::{
 };
 use rustc_lint::LateContext;
 use rustc_middle::hir::nested_filter;
-use rustc_middle::ty::{self, AssocKind, ClauseKind, EarlyBinder, GenericArg, GenericArgKind, Ty};
+use rustc_middle::ty::{self, AssocTag, ClauseKind, EarlyBinder, GenericArg, GenericArgKind, Ty};
 use rustc_span::symbol::Ident;
 use rustc_span::{Span, sym};
 
@@ -241,7 +241,7 @@ fn is_contains_sig(cx: &LateContext<'_>, call_id: HirId, iter_expr: &Expr<'_>) -
         && let Some(iter_item) = cx.tcx.associated_items(iter_trait).find_by_ident_and_kind(
             cx.tcx,
             Ident::with_dummy_span(sym::Item),
-            AssocKind::Type,
+            AssocTag::Type,
             iter_trait,
         )
         && let args = cx.tcx.mk_args(&[GenericArg::from(typeck.expr_ty_adjusted(iter_expr))])
diff --git a/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs b/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
index c03420a5143e6..6eeeea5d77c70 100644
--- a/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
@@ -78,7 +78,7 @@ pub(super) fn check<'tcx>(
                 .iter()
                 .flat_map(|impl_id| cx.tcx.associated_items(impl_id).filter_by_name_unhygienic(sugg))
                 .find_map(|assoc| {
-                    if assoc.fn_has_self_parameter
+                    if assoc.is_method()
                         && cx.tcx.fn_sig(assoc.def_id).skip_binder().inputs().skip_binder().len() == 1
                     {
                         Some(assoc.def_id)
diff --git a/src/tools/clippy/clippy_lints/src/needless_borrows_for_generic_args.rs b/src/tools/clippy/clippy_lints/src/needless_borrows_for_generic_args.rs
index f686cc912ddb0..e579dd5947d74 100644
--- a/src/tools/clippy/clippy_lints/src/needless_borrows_for_generic_args.rs
+++ b/src/tools/clippy/clippy_lints/src/needless_borrows_for_generic_args.rs
@@ -299,7 +299,7 @@ fn has_ref_mut_self_method(cx: &LateContext<'_>, trait_def_id: DefId) -> bool {
         .associated_items(trait_def_id)
         .in_definition_order()
         .any(|assoc_item| {
-            if assoc_item.fn_has_self_parameter {
+            if assoc_item.is_method() {
                 let self_ty = cx
                     .tcx
                     .fn_sig(assoc_item.def_id)
diff --git a/src/tools/clippy/clippy_lints/src/same_name_method.rs b/src/tools/clippy/clippy_lints/src/same_name_method.rs
index 552135b15fd8f..ae677e110af27 100644
--- a/src/tools/clippy/clippy_lints/src/same_name_method.rs
+++ b/src/tools/clippy/clippy_lints/src/same_name_method.rs
@@ -3,7 +3,6 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{HirId, Impl, ItemKind, Node, Path, QPath, TraitRef, TyKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::AssocKind;
 use rustc_session::declare_lint_pass;
 use rustc_span::Span;
 use rustc_span::symbol::Symbol;
@@ -85,7 +84,7 @@ impl<'tcx> LateLintPass<'tcx> for SameNameMethod {
                             cx.tcx
                                 .associated_items(did)
                                 .in_definition_order()
-                                .filter(|assoc_item| matches!(assoc_item.kind, AssocKind::Fn))
+                                .filter(|assoc_item| assoc_item.is_fn())
                                 .map(|assoc_item| assoc_item.name)
                                 .collect()
                         } else {
diff --git a/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs b/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
index 51c7d6fce3128..2104eb302ab88 100644
--- a/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
+++ b/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
@@ -10,7 +10,7 @@ use rustc_hir::{Body, Expr, ExprKind, FnDecl, HirId, Item, ItemKind, Node, QPath
 use rustc_hir_analysis::lower_ty;
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::nested_filter;
-use rustc_middle::ty::{self, AssocKind, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::impl_lint_pass;
 use rustc_span::symbol::{Ident, kw};
 use rustc_span::{Span, sym};
@@ -322,7 +322,7 @@ impl UnconditionalRecursion {
                             .in_definition_order()
                             // We're not interested in foreign implementations of the `Default` trait.
                             .find(|item| {
-                                item.kind == AssocKind::Fn && item.def_id.is_local() && item.name == kw::Default
+                                item.is_fn() && item.def_id.is_local() && item.name == kw::Default
                             })
                         && let Some(body_node) = cx.tcx.hir_get_if_local(assoc_item.def_id)
                         && let Some(body_id) = body_node.body_id()
diff --git a/src/tools/clippy/clippy_lints/src/unused_self.rs b/src/tools/clippy/clippy_lints/src/unused_self.rs
index 582aa6e6001e8..d0067b1a65e71 100644
--- a/src/tools/clippy/clippy_lints/src/unused_self.rs
+++ b/src/tools/clippy/clippy_lints/src/unused_self.rs
@@ -74,7 +74,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedSelf {
             .is_some()
         };
         if let ItemKind::Impl(Impl { of_trait: None, .. }) = parent_item.kind
-            && assoc_item.fn_has_self_parameter
+            && assoc_item.is_method()
             && let ImplItemKind::Fn(.., body_id) = &impl_item.kind
             && (!cx.effective_visibilities.is_exported(impl_item.owner_id.def_id) || !self.avoid_breaking_exported_api)
             && let body = cx.tcx.hir_body(*body_id)
diff --git a/src/tools/clippy/clippy_utils/src/ty/mod.rs b/src/tools/clippy/clippy_utils/src/ty/mod.rs
index 3779e2f306235..d33e59342a598 100644
--- a/src/tools/clippy/clippy_utils/src/ty/mod.rs
+++ b/src/tools/clippy/clippy_utils/src/ty/mod.rs
@@ -19,7 +19,7 @@ use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::traits::EvaluationResult;
 use rustc_middle::ty::layout::ValidityRequirement;
 use rustc_middle::ty::{
-    self, AdtDef, AliasTy, AssocItem, AssocKind, Binder, BoundRegion, FnSig, GenericArg, GenericArgKind,
+    self, AdtDef, AliasTy, AssocItem, AssocTag, Binder, BoundRegion, FnSig, GenericArg, GenericArgKind,
     GenericArgsRef, GenericParamDefKind, IntTy, ParamEnv, Region, RegionKind, TraitRef, Ty, TyCtxt, TypeSuperVisitable,
     TypeVisitable, TypeVisitableExt, TypeVisitor, UintTy, Upcast, VariantDef, VariantDiscr,
 };
@@ -1112,7 +1112,7 @@ pub fn make_projection<'tcx>(
         let Some(assoc_item) = tcx.associated_items(container_id).find_by_ident_and_kind(
             tcx,
             Ident::with_dummy_span(assoc_ty),
-            AssocKind::Type,
+            AssocTag::Type,
             container_id,
         ) else {
             debug_assert!(false, "type `{assoc_ty}` not found in `{container_id:?}`");
@@ -1345,7 +1345,7 @@ pub fn get_adt_inherent_method<'a>(cx: &'a LateContext<'_>, ty: Ty<'_>, method_n
                 .associated_items(did)
                 .filter_by_name_unhygienic(method_name)
                 .next()
-                .filter(|item| item.kind == AssocKind::Fn)
+                .filter(|item| item.as_tag() == AssocTag::Fn)
         })
     } else {
         None
diff --git a/tests/ui/generic-associated-types/impl_bounds.stderr b/tests/ui/generic-associated-types/impl_bounds.stderr
index 231c0dd89c52d..7847bbd813cd5 100644
--- a/tests/ui/generic-associated-types/impl_bounds.stderr
+++ b/tests/ui/generic-associated-types/impl_bounds.stderr
@@ -57,14 +57,14 @@ note: required for `Fooy<T>` to implement `Copy`
    |
 LL | #[derive(Copy, Clone)]
    |          ^^^^ unsatisfied trait bound introduced in this `derive` macro
-note: the requirement `Fooy<T>: Copy` appears on the `impl`'s method `d` but not on the corresponding trait's method
+note: the requirement `Fooy<T>: Copy` appears on the `impl`'s associated function `d` but not on the corresponding trait's associated function
   --> $DIR/impl_bounds.rs:7:8
    |
 LL | trait Foo {
    |       --- in this trait
 ...
 LL |     fn d() where Self: Clone;
-   |        ^ this trait's method doesn't have the requirement `Fooy<T>: Copy`
+   |        ^ this trait's associated function doesn't have the requirement `Fooy<T>: Copy`
 help: consider restricting type parameter `T` with trait `Copy`
    |
 LL | impl<T: std::marker::Copy> Foo for Fooy<T> {
diff --git a/tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr b/tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr
index 74a0a90885da5..d179c80596238 100644
--- a/tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr
+++ b/tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr
@@ -4,14 +4,14 @@ error[E0275]: overflow evaluating the requirement `<() as A<T>>::Assoc: A<T>`
 LL |         Self::Assoc: A<T>,
    |                      ^^^^
    |
-note: the requirement `<() as A<T>>::Assoc: A<T>` appears on the `impl`'s method `f` but not on the corresponding trait's method
+note: the requirement `<() as A<T>>::Assoc: A<T>` appears on the `impl`'s associated function `f` but not on the corresponding trait's associated function
   --> $DIR/normalize-param-env-2.rs:12:8
    |
 LL | trait A<T> {
    |       - in this trait
 ...
 LL |     fn f()
-   |        ^ this trait's method doesn't have the requirement `<() as A<T>>::Assoc: A<T>`
+   |        ^ this trait's associated function doesn't have the requirement `<() as A<T>>::Assoc: A<T>`
 
 error[E0275]: overflow evaluating the requirement `<() as A<T>>::Assoc: A<T>`
   --> $DIR/normalize-param-env-2.rs:24:22

From 1ac3d6bba71fce59939e6a4d50de98e289e87b9b Mon Sep 17 00:00:00 2001
From: "Eddy (Eduard) Stefes" <eduard.stefes@ibm.com>
Date: Mon, 14 Apr 2025 09:49:43 +0200
Subject: [PATCH 13/24] Let CStrings be either 1 or 2 byte aligned.

Some architectures (like s390x) require strings to be 2 byte aligned.
Therefor the section name will be marked with a .2  postfix on this
architectures.

Allowing a section name with a .1 or .2 postfix will make the test pass
on either platform.
---
 tests/assembly/cstring-merging.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/assembly/cstring-merging.rs b/tests/assembly/cstring-merging.rs
index 07f25d1e1a427..b5c530ac35d76 100644
--- a/tests/assembly/cstring-merging.rs
+++ b/tests/assembly/cstring-merging.rs
@@ -5,7 +5,7 @@
 
 use std::ffi::CStr;
 
-// CHECK: .section .rodata.str1.1,"aMS"
+// CHECK: .section .rodata.str1.{{[12]}},"aMS"
 // CHECK: .Lanon.{{.+}}:
 // CHECK-NEXT: .asciz "foo"
 #[unsafe(no_mangle)]

From 9c88eb6c4344cc2387900bb362f09291f031e9c2 Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Mon, 14 Apr 2025 14:46:48 +0200
Subject: [PATCH 14/24] normalize: prefer ParamEnv over AliasBound

---
 .../src/solve/assembly/mod.rs                 | 51 +++++++++++--------
 .../norm-where-bound-gt-alias-bound.rs        | 29 +++++++++++
 2 files changed, 59 insertions(+), 21 deletions(-)
 create mode 100644 tests/ui/traits/winnowing/norm-where-bound-gt-alias-bound.rs

diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
index 384a304c4a9d6..ee000b1174866 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
@@ -792,37 +792,46 @@ where
         };
 
         match proven_via {
-            // Even when a trait bound has been proven using a where-bound, we
-            // still need to consider alias-bounds for normalization, see
-            // tests/ui/next-solver/alias-bound-shadowed-by-env.rs.
-            //
-            // FIXME(const_trait_impl): should this behavior also be used by
-            // constness checking. Doing so is *at least theoretically* breaking,
-            // see github.com/rust-lang/rust/issues/133044#issuecomment-2500709754
             TraitGoalProvenVia::ParamEnv | TraitGoalProvenVia::AliasBound => {
-                let mut candidates_from_env_and_bounds: Vec<_> = candidates
-                    .iter()
-                    .filter(|c| {
-                        matches!(
-                            c.source,
-                            CandidateSource::AliasBound | CandidateSource::ParamEnv(_)
-                        )
-                    })
-                    .map(|c| c.result)
-                    .collect();
+                let mut considered_candidates = Vec::new();
+                considered_candidates.extend(
+                    candidates
+                        .iter()
+                        .filter(|c| matches!(c.source, CandidateSource::ParamEnv(_)))
+                        .map(|c| c.result),
+                );
+
+                // Even when a trait bound has been proven using a where-bound, we
+                // still need to consider alias-bounds for normalization, see
+                // tests/ui/next-solver/alias-bound-shadowed-by-env.rs.
+                //
+                // We still need to prefer where-bounds over alias-bounds however.
+                // See tests/ui/winnowing/norm-where-bound-gt-alias-bound.rs.
+                //
+                // FIXME(const_trait_impl): should this behavior also be used by
+                // constness checking. Doing so is *at least theoretically* breaking,
+                // see github.com/rust-lang/rust/issues/133044#issuecomment-2500709754
+                if considered_candidates.is_empty() {
+                    considered_candidates.extend(
+                        candidates
+                            .iter()
+                            .filter(|c| matches!(c.source, CandidateSource::AliasBound))
+                            .map(|c| c.result),
+                    );
+                }
 
                 // If the trait goal has been proven by using the environment, we want to treat
                 // aliases as rigid if there are no applicable projection bounds in the environment.
-                if candidates_from_env_and_bounds.is_empty() {
+                if considered_candidates.is_empty() {
                     if let Ok(response) = inject_normalize_to_rigid_candidate(self) {
-                        candidates_from_env_and_bounds.push(response);
+                        considered_candidates.push(response);
                     }
                 }
 
-                if let Some(response) = self.try_merge_responses(&candidates_from_env_and_bounds) {
+                if let Some(response) = self.try_merge_responses(&considered_candidates) {
                     Ok(response)
                 } else {
-                    self.flounder(&candidates_from_env_and_bounds)
+                    self.flounder(&considered_candidates)
                 }
             }
             TraitGoalProvenVia::Misc => {
diff --git a/tests/ui/traits/winnowing/norm-where-bound-gt-alias-bound.rs b/tests/ui/traits/winnowing/norm-where-bound-gt-alias-bound.rs
new file mode 100644
index 0000000000000..cdfb0ee45af4d
--- /dev/null
+++ b/tests/ui/traits/winnowing/norm-where-bound-gt-alias-bound.rs
@@ -0,0 +1,29 @@
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+//@ check-pass
+
+// Make sure we prefer the `I::IntoIterator: Iterator<Item = ()>`
+// where-bound over the `I::Intoiterator: Iterator<Item = I::Item>`
+// alias-bound.
+
+trait Iterator {
+    type Item;
+}
+
+trait IntoIterator {
+    type Item;
+    type IntoIter: Iterator<Item = Self::Item>;
+}
+
+fn normalize<I: Iterator<Item = ()>>() {}
+
+fn foo<I>()
+where
+    I: IntoIterator,
+    I::IntoIter: Iterator<Item = ()>,
+{
+    normalize::<I::IntoIter>();
+}
+
+fn main() {}

From 1b46969a11b2cfa000593b225af94a9d3bfbedfc Mon Sep 17 00:00:00 2001
From: clubby789 <jamie@hill-daniel.co.uk>
Date: Mon, 14 Apr 2025 14:16:30 +0100
Subject: [PATCH 15/24] Specify `--print info=file` syntax in `--help`

---
 compiler/rustc_session/src/config.rs               | 14 ++++----------
 tests/run-make/rustc-help/help-v.diff              |  2 +-
 tests/run-make/rustc-help/help-v.stdout            |  6 ++++--
 tests/run-make/rustc-help/help.stdout              |  6 ++++--
 .../invalid-compile-flags/print-without-arg.stderr |  5 +++--
 5 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index bdd54a15147b4..fc05470d941c4 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -1560,9 +1560,10 @@ The default is {DEFAULT_EDITION} and the latest stable edition is {LATEST_STABLE
     )
 });
 
-static PRINT_KINDS_STRING: LazyLock<String> = LazyLock::new(|| {
+static PRINT_HELP: LazyLock<String> = LazyLock::new(|| {
     format!(
-        "[{}]",
+        "Compiler information to print on stdout (or to a file)\n\
+        INFO may be one of ({}).",
         PRINT_KINDS.iter().map(|(name, _)| format!("{name}")).collect::<Vec<_>>().join("|")
     )
 });
@@ -1621,14 +1622,7 @@ pub fn rustc_optgroups() -> Vec<RustcOptGroup> {
             "Comma separated list of types of output for the compiler to emit",
             "[asm|llvm-bc|llvm-ir|obj|metadata|link|dep-info|mir]",
         ),
-        opt(
-            Stable,
-            Multi,
-            "",
-            "print",
-            "Compiler information to print on stdout",
-            &PRINT_KINDS_STRING,
-        ),
+        opt(Stable, Multi, "", "print", &PRINT_HELP, "INFO[=FILE]"),
         opt(Stable, FlagMulti, "g", "", "Equivalent to -C debuginfo=2", ""),
         opt(Stable, FlagMulti, "O", "", "Equivalent to -C opt-level=3", ""),
         opt(Stable, Opt, "o", "", "Write output to <filename>", "FILENAME"),
diff --git a/tests/run-make/rustc-help/help-v.diff b/tests/run-make/rustc-help/help-v.diff
index 22c5dd81bdb05..30703f6424e7e 100644
--- a/tests/run-make/rustc-help/help-v.diff
+++ b/tests/run-make/rustc-help/help-v.diff
@@ -1,4 +1,4 @@
-@@ -51,10 +51,27 @@
+@@ -53,10 +53,27 @@
                          Set a codegen option
      -V, --version       Print version info and exit
      -v, --verbose       Use verbose output
diff --git a/tests/run-make/rustc-help/help-v.stdout b/tests/run-make/rustc-help/help-v.stdout
index f19ca1e9f90ab..13af6e21060b5 100644
--- a/tests/run-make/rustc-help/help-v.stdout
+++ b/tests/run-make/rustc-help/help-v.stdout
@@ -29,8 +29,10 @@ Options:
         --emit [asm|llvm-bc|llvm-ir|obj|metadata|link|dep-info|mir]
                         Comma separated list of types of output for the
                         compiler to emit
-        --print [all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models]
-                        Compiler information to print on stdout
+        --print INFO[=FILE]
+                        Compiler information to print on stdout (or to a file)
+                        INFO may be one of
+                        (all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models).
     -g                  Equivalent to -C debuginfo=2
     -O                  Equivalent to -C opt-level=3
     -o FILENAME         Write output to <filename>
diff --git a/tests/run-make/rustc-help/help.stdout b/tests/run-make/rustc-help/help.stdout
index f7d352966035b..62757d989eb3b 100644
--- a/tests/run-make/rustc-help/help.stdout
+++ b/tests/run-make/rustc-help/help.stdout
@@ -29,8 +29,10 @@ Options:
         --emit [asm|llvm-bc|llvm-ir|obj|metadata|link|dep-info|mir]
                         Comma separated list of types of output for the
                         compiler to emit
-        --print [all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models]
-                        Compiler information to print on stdout
+        --print INFO[=FILE]
+                        Compiler information to print on stdout (or to a file)
+                        INFO may be one of
+                        (all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models).
     -g                  Equivalent to -C debuginfo=2
     -O                  Equivalent to -C opt-level=3
     -o FILENAME         Write output to <filename>
diff --git a/tests/ui/invalid-compile-flags/print-without-arg.stderr b/tests/ui/invalid-compile-flags/print-without-arg.stderr
index 8abaee5056bab..fd2a36e761bef 100644
--- a/tests/ui/invalid-compile-flags/print-without-arg.stderr
+++ b/tests/ui/invalid-compile-flags/print-without-arg.stderr
@@ -1,5 +1,6 @@
 error: Argument to option 'print' missing
        Usage:
-           --print [all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models]
-                               Compiler information to print on stdout
+           --print INFO[=FILE] Compiler information to print on stdout (or to a file)
+                               INFO may be one of
+                               (all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models).
 

From 1f3199c89995ee7ae5cbdaa81d1df5138660d61a Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Mon, 14 Apr 2025 16:53:24 +0200
Subject: [PATCH 16/24] Disable some r-a tests in bootstrap.

---
 src/tools/rust-analyzer/crates/proc-macro-srv/src/tests/mod.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/tools/rust-analyzer/crates/proc-macro-srv/src/tests/mod.rs b/src/tools/rust-analyzer/crates/proc-macro-srv/src/tests/mod.rs
index 15de88ea656d0..4bd365be7ca8b 100644
--- a/src/tools/rust-analyzer/crates/proc-macro-srv/src/tests/mod.rs
+++ b/src/tools/rust-analyzer/crates/proc-macro-srv/src/tests/mod.rs
@@ -97,6 +97,7 @@ fn test_fn_like_macro_clone_raw_ident() {
 }
 
 #[test]
+#[cfg(not(bootstrap))]
 fn test_fn_like_fn_like_span_join() {
     assert_expand(
         "fn_like_span_join",
@@ -111,6 +112,7 @@ fn test_fn_like_fn_like_span_join() {
 }
 
 #[test]
+#[cfg(not(bootstrap))]
 fn test_fn_like_fn_like_span_ops() {
     assert_expand(
         "fn_like_span_ops",

From 758e99a8004cf30c35a5dc17d9f8c626fc4ae2c9 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Mon, 14 Apr 2025 17:43:14 +0200
Subject: [PATCH 17/24] update lockfile

---
 Cargo.lock | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 41288c55fe59a..0e5d6281d672d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2046,9 +2046,9 @@ dependencies = [
 
 [[package]]
 name = "libffi"
-version = "3.2.0"
+version = "4.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ce826c243048e3d5cec441799724de52e2d42f820468431fc3fceee2341871e2"
+checksum = "4a9434b6fc77375fb624698d5f8c49d7e80b10d59eb1219afda27d1f824d4074"
 dependencies = [
  "libc",
  "libffi-sys",
@@ -2056,9 +2056,9 @@ dependencies = [
 
 [[package]]
 name = "libffi-sys"
-version = "2.3.0"
+version = "3.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f36115160c57e8529781b4183c2bb51fdc1f6d6d1ed345591d84be7703befb3c"
+checksum = "ead36a2496acfc8edd6cc32352110e9478ac5b9b5f5b9856ebd3d28019addb84"
 dependencies = [
  "cc",
 ]

From 4b63362f3d0a455707f64ce345ca3a5467b04764 Mon Sep 17 00:00:00 2001
From: Yotam Ofek <yotam.ofek@gmail.com>
Date: Mon, 14 Apr 2025 15:52:25 +0000
Subject: [PATCH 18/24] Use `newtype_index!`-generated types more idiomatically

---
 compiler/rustc_ast_lowering/src/path.rs       |  3 +--
 .../rustc_borrowck/src/region_infer/mod.rs    |  3 +--
 .../src/debuginfo/create_scope_map.rs         |  4 +--
 compiler/rustc_hir/src/definitions.rs         |  9 +++----
 .../src/check/compare_impl_item.rs            |  7 ++---
 .../src/infer/region_constraints/mod.rs       |  4 +--
 .../rustc_infer/src/infer/snapshot/fudge.rs   |  7 ++---
 compiler/rustc_middle/src/mir/pretty.rs       |  6 ++---
 compiler/rustc_middle/src/ty/fold.rs          |  2 +-
 compiler/rustc_middle/src/ty/visit.rs         | 12 +++------
 compiler/rustc_mir_build/src/thir/cx/expr.rs  |  4 +--
 compiler/rustc_mir_transform/src/coroutine.rs |  4 +--
 .../rustc_mir_transform/src/elaborate_drop.rs | 17 ++++++------
 compiler/rustc_mir_transform/src/inline.rs    | 12 ++++-----
 compiler/rustc_mir_transform/src/patch.rs     |  2 +-
 .../rustc_mir_transform/src/promote_consts.rs | 14 ++++++----
 .../src/solve/eval_ctxt/canonical.rs          |  2 +-
 compiler/rustc_passes/src/liveness.rs         |  7 +++--
 compiler/rustc_resolve/src/late.rs            |  2 +-
 .../rustc_trait_selection/src/traits/mod.rs   | 27 ++++++-------------
 20 files changed, 61 insertions(+), 87 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index c464c159c34cd..0bd65aec10f49 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -448,8 +448,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         generic_args.args.insert_many(
             0,
-            (start.as_u32()..end.as_u32()).map(|i| {
-                let id = NodeId::from_u32(i);
+            (start..end).map(|id| {
                 let l = self.lower_lifetime_anon_in_path(id, elided_lifetime_span);
                 GenericArg::Lifetime(l)
             }),
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index c82c7341f0287..f8af9e59f6357 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -338,8 +338,7 @@ fn sccs_info<'tcx>(infcx: &BorrowckInferCtxt<'tcx>, sccs: &ConstraintSccs) {
     let num_components = sccs.num_sccs();
     let mut components = vec![FxIndexSet::default(); num_components];
 
-    for (reg_var_idx, scc_idx) in sccs.scc_indices().iter().enumerate() {
-        let reg_var = ty::RegionVid::from_usize(reg_var_idx);
+    for (reg_var, scc_idx) in sccs.scc_indices().iter_enumerated() {
         let origin = var_to_origin.get(&reg_var).unwrap_or(&RegionCtxt::Unknown);
         components[scc_idx.as_usize()].insert((reg_var, *origin));
     }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs b/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
index f52991b369797..d2591139d6edc 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
@@ -3,7 +3,6 @@ use std::collections::hash_map::Entry;
 use rustc_codegen_ssa::mir::debuginfo::{DebugScope, FunctionDebugContext};
 use rustc_codegen_ssa::traits::*;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_index::Idx;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_middle::mir::{Body, SourceScope};
 use rustc_middle::ty::layout::{FnAbiOf, HasTypingEnv};
@@ -43,8 +42,7 @@ pub(crate) fn compute_mir_scopes<'ll, 'tcx>(
     let mut instantiated = DenseBitSet::new_empty(mir.source_scopes.len());
     let mut discriminators = FxHashMap::default();
     // Instantiate all scopes.
-    for idx in 0..mir.source_scopes.len() {
-        let scope = SourceScope::new(idx);
+    for scope in mir.source_scopes.indices() {
         make_mir_scope(
             cx,
             instance,
diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index 34f3c169505ff..bf7b1eefcf68c 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -47,12 +47,9 @@ impl DefPathTable {
         debug_assert_eq!(self.stable_crate_id, def_path_hash.stable_crate_id());
         let local_hash = def_path_hash.local_hash();
 
-        let index = {
-            let index = DefIndex::from(self.index_to_key.len());
-            debug!("DefPathTable::insert() - {:?} <-> {:?}", key, index);
-            self.index_to_key.push(key);
-            index
-        };
+        let index = self.index_to_key.push(key);
+        debug!("DefPathTable::insert() - {key:?} <-> {index:?}");
+
         self.def_path_hashes.push(local_hash);
         debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
 
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 29a9931696ffa..106e9ca155489 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -606,7 +606,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     // with placeholders, which imply nothing about outlives bounds, and then
     // prove below that the hidden types are well formed.
     let universe = infcx.create_next_universe();
-    let mut idx = 0;
+    let mut idx = ty::BoundVar::ZERO;
     let mapping: FxIndexMap<_, _> = collector
         .types
         .iter()
@@ -623,10 +623,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
                     tcx,
                     ty::Placeholder {
                         universe,
-                        bound: ty::BoundTy {
-                            var: ty::BoundVar::from_usize(idx),
-                            kind: ty::BoundTyKind::Anon,
-                        },
+                        bound: ty::BoundTy { var: idx, kind: ty::BoundTyKind::Anon },
                     },
                 ),
             )
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 8366aa6ec4228..40e2e654b2ea7 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -618,9 +618,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
             RegionVid::from(value_count)..RegionVid::from(self.storage.unification_table.len());
         (
             range.clone(),
-            (range.start.index()..range.end.index())
-                .map(|index| self.storage.var_infos[ty::RegionVid::from(index)].origin)
-                .collect(),
+            (range.start..range.end).map(|index| self.storage.var_infos[index].origin).collect(),
         )
     }
 
diff --git a/compiler/rustc_infer/src/infer/snapshot/fudge.rs b/compiler/rustc_infer/src/infer/snapshot/fudge.rs
index b5d3c26b05e0b..39c8c40ea7d8b 100644
--- a/compiler/rustc_infer/src/infer/snapshot/fudge.rs
+++ b/compiler/rustc_infer/src/infer/snapshot/fudge.rs
@@ -30,11 +30,12 @@ fn const_vars_since_snapshot<'tcx>(
     snapshot_var_len: usize,
 ) -> (Range<ConstVid>, Vec<ConstVariableOrigin>) {
     let range = vars_since_snapshot(table, snapshot_var_len);
+    let range = range.start.vid..range.end.vid;
 
     (
-        range.start.vid..range.end.vid,
-        (range.start.index()..range.end.index())
-            .map(|index| match table.probe_value(ConstVid::from_u32(index)) {
+        range.clone(),
+        range
+            .map(|index| match table.probe_value(index) {
                 ConstVariableValue::Known { value: _ } => {
                     ConstVariableOrigin { param_def_id: None, span: rustc_span::DUMMY_SP }
                 }
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index 5a038b27337cf..e7bd2cb27fa75 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -531,12 +531,12 @@ fn write_mir_intro<'tcx>(
 
     // construct a scope tree and write it out
     let mut scope_tree: FxHashMap<SourceScope, Vec<SourceScope>> = Default::default();
-    for (index, scope_data) in body.source_scopes.iter().enumerate() {
+    for (index, scope_data) in body.source_scopes.iter_enumerated() {
         if let Some(parent) = scope_data.parent_scope {
-            scope_tree.entry(parent).or_default().push(SourceScope::new(index));
+            scope_tree.entry(parent).or_default().push(index);
         } else {
             // Only the argument scope has no parent, because it's the root.
-            assert_eq!(index, OUTERMOST_SOURCE_SCOPE.index());
+            assert_eq!(index, OUTERMOST_SOURCE_SCOPE);
         }
     }
 
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 8dc73e4ce85ee..8d6871d2f1fee 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -278,7 +278,7 @@ impl<'tcx> TyCtxt<'tcx> {
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
-        let shift_bv = |bv: ty::BoundVar| ty::BoundVar::from_usize(bv.as_usize() + bound_vars);
+        let shift_bv = |bv: ty::BoundVar| bv + bound_vars;
         self.replace_escaping_bound_vars_uncached(
             value,
             FnMutDelegate {
diff --git a/compiler/rustc_middle/src/ty/visit.rs b/compiler/rustc_middle/src/ty/visit.rs
index b341b30af6acf..44c7b6a7c9e8d 100644
--- a/compiler/rustc_middle/src/ty/visit.rs
+++ b/compiler/rustc_middle/src/ty/visit.rs
@@ -231,9 +231,7 @@ impl MaxUniverse {
 impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
     fn visit_ty(&mut self, t: Ty<'tcx>) {
         if let ty::Placeholder(placeholder) = t.kind() {
-            self.max_universe = ty::UniverseIndex::from_u32(
-                self.max_universe.as_u32().max(placeholder.universe.as_u32()),
-            );
+            self.max_universe = self.max_universe.max(placeholder.universe);
         }
 
         t.super_visit_with(self)
@@ -241,9 +239,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
 
     fn visit_const(&mut self, c: ty::consts::Const<'tcx>) {
         if let ty::ConstKind::Placeholder(placeholder) = c.kind() {
-            self.max_universe = ty::UniverseIndex::from_u32(
-                self.max_universe.as_u32().max(placeholder.universe.as_u32()),
-            );
+            self.max_universe = self.max_universe.max(placeholder.universe);
         }
 
         c.super_visit_with(self)
@@ -251,9 +247,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
 
     fn visit_region(&mut self, r: ty::Region<'tcx>) {
         if let ty::RePlaceholder(placeholder) = r.kind() {
-            self.max_universe = ty::UniverseIndex::from_u32(
-                self.max_universe.as_u32().max(placeholder.universe.as_u32()),
-            );
+            self.max_universe = self.max_universe.max(placeholder.universe);
         }
     }
 }
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 31e22e69111be..fde23413972b6 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -191,7 +191,7 @@ impl<'tcx> ThirBuildCx<'tcx> {
                 let pointer_target = ExprKind::Field {
                     lhs: self.thir.exprs.push(expr),
                     variant_index: FIRST_VARIANT,
-                    name: FieldIdx::from(0u32),
+                    name: FieldIdx::ZERO,
                 };
                 let arg = Expr { temp_lifetime, ty: pin_ty, span, kind: pointer_target };
                 let arg = self.thir.exprs.push(arg);
@@ -226,7 +226,7 @@ impl<'tcx> ThirBuildCx<'tcx> {
                     adt_def: self.tcx.adt_def(pin_did),
                     variant_index: FIRST_VARIANT,
                     args,
-                    fields: Box::new([FieldExpr { name: FieldIdx::from(0u32), expr }]),
+                    fields: Box::new([FieldExpr { name: FieldIdx::ZERO, expr }]),
                     user_ty: None,
                     base: AdtExprBase::None,
                 }));
diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs
index 4405bd82410e3..92d5e152f58e6 100644
--- a/compiler/rustc_mir_transform/src/coroutine.rs
+++ b/compiler/rustc_mir_transform/src/coroutine.rs
@@ -203,7 +203,7 @@ struct TransformVisitor<'tcx> {
 
 impl<'tcx> TransformVisitor<'tcx> {
     fn insert_none_ret_block(&self, body: &mut Body<'tcx>) -> BasicBlock {
-        let block = BasicBlock::new(body.basic_blocks.len());
+        let block = body.basic_blocks.next_index();
         let source_info = SourceInfo::outermost(body.span);
 
         let none_value = match self.coroutine_kind {
@@ -1193,7 +1193,7 @@ fn insert_panic_block<'tcx>(
     body: &mut Body<'tcx>,
     message: AssertMessage<'tcx>,
 ) -> BasicBlock {
-    let assert_block = BasicBlock::new(body.basic_blocks.len());
+    let assert_block = body.basic_blocks.next_index();
     let kind = TerminatorKind::Assert {
         cond: Operand::Constant(Box::new(ConstOperand {
             span: body.span,
diff --git a/compiler/rustc_mir_transform/src/elaborate_drop.rs b/compiler/rustc_mir_transform/src/elaborate_drop.rs
index fa476f961235d..e3057a2f648f2 100644
--- a/compiler/rustc_mir_transform/src/elaborate_drop.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_drop.rs
@@ -258,17 +258,16 @@ where
     ) -> Vec<(Place<'tcx>, Option<D::Path>)> {
         variant
             .fields
-            .iter()
-            .enumerate()
-            .map(|(i, f)| {
-                let field = FieldIdx::new(i);
-                let subpath = self.elaborator.field_subpath(variant_path, field);
+            .iter_enumerated()
+            .map(|(field_idx, field)| {
+                let subpath = self.elaborator.field_subpath(variant_path, field_idx);
                 let tcx = self.tcx();
 
                 assert_eq!(self.elaborator.typing_env().typing_mode, ty::TypingMode::PostAnalysis);
-                let field_ty = match tcx
-                    .try_normalize_erasing_regions(self.elaborator.typing_env(), f.ty(tcx, args))
-                {
+                let field_ty = match tcx.try_normalize_erasing_regions(
+                    self.elaborator.typing_env(),
+                    field.ty(tcx, args),
+                ) {
                     Ok(t) => t,
                     Err(_) => Ty::new_error(
                         self.tcx(),
@@ -279,7 +278,7 @@ where
                     ),
                 };
 
-                (tcx.mk_place_field(base_place, field, field_ty), subpath)
+                (tcx.mk_place_field(base_place, field_idx, field_ty), subpath)
             })
             .collect()
     }
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 0ab24e48d443c..69e80ed54eae7 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -903,9 +903,9 @@ fn inline_call<'tcx, I: Inliner<'tcx>>(
 
     let mut integrator = Integrator {
         args: &args,
-        new_locals: Local::new(caller_body.local_decls.len())..,
-        new_scopes: SourceScope::new(caller_body.source_scopes.len())..,
-        new_blocks: BasicBlock::new(caller_body.basic_blocks.len())..,
+        new_locals: caller_body.local_decls.next_index()..,
+        new_scopes: caller_body.source_scopes.next_index()..,
+        new_blocks: caller_body.basic_blocks.next_index()..,
         destination: destination_local,
         callsite_scope: caller_body.source_scopes[callsite.source_info.scope].clone(),
         callsite,
@@ -1169,7 +1169,7 @@ impl Integrator<'_, '_> {
             if idx < self.args.len() {
                 self.args[idx]
             } else {
-                Local::new(self.new_locals.start.index() + (idx - self.args.len()))
+                self.new_locals.start + (idx - self.args.len())
             }
         };
         trace!("mapping local `{:?}` to `{:?}`", local, new);
@@ -1177,13 +1177,13 @@ impl Integrator<'_, '_> {
     }
 
     fn map_scope(&self, scope: SourceScope) -> SourceScope {
-        let new = SourceScope::new(self.new_scopes.start.index() + scope.index());
+        let new = self.new_scopes.start + scope.index();
         trace!("mapping scope `{:?}` to `{:?}`", scope, new);
         new
     }
 
     fn map_block(&self, block: BasicBlock) -> BasicBlock {
-        let new = BasicBlock::new(self.new_blocks.start.index() + block.index());
+        let new = self.new_blocks.start + block.index();
         trace!("mapping block `{:?}` to `{:?}`", block, new);
         new
     }
diff --git a/compiler/rustc_mir_transform/src/patch.rs b/compiler/rustc_mir_transform/src/patch.rs
index 6a177faeac81f..12ace04c5e267 100644
--- a/compiler/rustc_mir_transform/src/patch.rs
+++ b/compiler/rustc_mir_transform/src/patch.rs
@@ -181,7 +181,7 @@ impl<'tcx> MirPatch<'tcx> {
 
     /// Queues the addition of a new basic block.
     pub(crate) fn new_block(&mut self, data: BasicBlockData<'tcx>) -> BasicBlock {
-        let block = BasicBlock::new(self.term_patch_map.len());
+        let block = self.term_patch_map.next_index();
         debug!("MirPatch: new_block: {:?}: {:?}", block, data);
         self.new_blocks.push(data);
         self.term_patch_map.push(None);
diff --git a/compiler/rustc_mir_transform/src/promote_consts.rs b/compiler/rustc_mir_transform/src/promote_consts.rs
index c8d8dc147e94f..47d4383097008 100644
--- a/compiler/rustc_mir_transform/src/promote_consts.rs
+++ b/compiler/rustc_mir_transform/src/promote_consts.rs
@@ -18,7 +18,7 @@ use either::{Left, Right};
 use rustc_const_eval::check_consts::{ConstCx, qualifs};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
-use rustc_index::{Idx, IndexSlice, IndexVec};
+use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, GenericArgs, List, Ty, TyCtxt, TypeVisitableExt};
@@ -864,17 +864,21 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
         new_temp
     }
 
-    fn promote_candidate(mut self, candidate: Candidate, next_promoted_id: usize) -> Body<'tcx> {
+    fn promote_candidate(
+        mut self,
+        candidate: Candidate,
+        next_promoted_index: Promoted,
+    ) -> Body<'tcx> {
         let def = self.source.source.def_id();
         let (mut rvalue, promoted_op) = {
             let promoted = &mut self.promoted;
-            let promoted_id = Promoted::new(next_promoted_id);
             let tcx = self.tcx;
             let mut promoted_operand = |ty, span| {
                 promoted.span = span;
                 promoted.local_decls[RETURN_PLACE] = LocalDecl::new(ty, span);
                 let args = tcx.erase_regions(GenericArgs::identity_for_item(tcx, def));
-                let uneval = mir::UnevaluatedConst { def, args, promoted: Some(promoted_id) };
+                let uneval =
+                    mir::UnevaluatedConst { def, args, promoted: Some(next_promoted_index) };
 
                 ConstOperand { span, user_ty: None, const_: Const::Unevaluated(uneval, ty) }
             };
@@ -1034,7 +1038,7 @@ fn promote_candidates<'tcx>(
             required_consts: Vec::new(),
         };
 
-        let mut promoted = promoter.promote_candidate(candidate, promotions.len());
+        let mut promoted = promoter.promote_candidate(candidate, promotions.next_index());
         promoted.source.promoted = Some(promotions.next_index());
         promotions.push(promoted);
     }
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
index 4edc293ad807d..d56b0e5847e57 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
@@ -355,7 +355,7 @@ where
                     // exist at all (see the FIXME at the start of this method), we have to deal with
                     // them for now.
                     delegate.instantiate_canonical_var_with_infer(info, span, |idx| {
-                        ty::UniverseIndex::from(prev_universe.index() + idx.index())
+                        prev_universe + idx.index()
                     })
                 } else if info.is_existential() {
                     // As an optimization we sometimes avoid creating a new inference variable here.
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 06eb76c30c5fb..7054bbf468b9b 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -578,8 +578,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
     where
         F: FnMut(Variable) -> bool,
     {
-        for var_idx in 0..self.ir.var_kinds.len() {
-            let var = Variable::from(var_idx);
+        for var in self.ir.var_kinds.indices() {
             if test(var) {
                 write!(wr, " {var:?}")?;
             }
@@ -609,8 +608,8 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         debug!(
             "^^ liveness computation results for body {} (entry={:?})",
             {
-                for ln_idx in 0..self.ir.lnks.len() {
-                    debug!("{:?}", self.ln_str(LiveNode::from(ln_idx)));
+                for ln_idx in self.ir.lnks.indices() {
+                    debug!("{:?}", self.ln_str(ln_idx));
                 }
                 hir_id
             },
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index a7170edb98673..13de816848844 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -1948,7 +1948,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
 
         self.record_lifetime_res(
             anchor_id,
-            LifetimeRes::ElidedAnchor { start: id, end: NodeId::from_u32(id.as_u32() + 1) },
+            LifetimeRes::ElidedAnchor { start: id, end: id + 1 },
             LifetimeElisionCandidate::Ignore,
         );
         self.resolve_anonymous_lifetime(&lt, anchor_id, true);
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index de337710b5ef7..8ac8dc67fbd81 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -643,7 +643,7 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
 ) -> GenericArgsRef<'tcx> {
     struct ReplaceParamAndInferWithPlaceholder<'tcx> {
         tcx: TyCtxt<'tcx>,
-        idx: u32,
+        idx: ty::BoundVar,
     }
 
     impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReplaceParamAndInferWithPlaceholder<'tcx> {
@@ -653,19 +653,13 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
 
         fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
             if let ty::Infer(_) = t.kind() {
-                let idx = {
-                    let idx = self.idx;
-                    self.idx += 1;
-                    idx
-                };
+                let idx = self.idx;
+                self.idx += 1;
                 Ty::new_placeholder(
                     self.tcx,
                     ty::PlaceholderType {
                         universe: ty::UniverseIndex::ROOT,
-                        bound: ty::BoundTy {
-                            var: ty::BoundVar::from_u32(idx),
-                            kind: ty::BoundTyKind::Anon,
-                        },
+                        bound: ty::BoundTy { var: idx, kind: ty::BoundTyKind::Anon },
                     },
                 )
             } else {
@@ -675,16 +669,11 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
 
         fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> {
             if let ty::ConstKind::Infer(_) = c.kind() {
+                let idx = self.idx;
+                self.idx += 1;
                 ty::Const::new_placeholder(
                     self.tcx,
-                    ty::PlaceholderConst {
-                        universe: ty::UniverseIndex::ROOT,
-                        bound: ty::BoundVar::from_u32({
-                            let idx = self.idx;
-                            self.idx += 1;
-                            idx
-                        }),
-                    },
+                    ty::PlaceholderConst { universe: ty::UniverseIndex::ROOT, bound: idx },
                 )
             } else {
                 c.super_fold_with(self)
@@ -692,7 +681,7 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
         }
     }
 
-    args.fold_with(&mut ReplaceParamAndInferWithPlaceholder { tcx, idx: 0 })
+    args.fold_with(&mut ReplaceParamAndInferWithPlaceholder { tcx, idx: ty::BoundVar::ZERO })
 }
 
 /// Normalizes the predicates and checks whether they hold in an empty environment. If this

From 188d44dd6e4949606e31c8009dffa4773ea25214 Mon Sep 17 00:00:00 2001
From: 0x79de <0x79de@gmail.com>
Date: Mon, 14 Apr 2025 21:25:48 +0300
Subject: [PATCH 19/24] Fix: Map EOPNOTSUPP to ErrorKind::Unsupported on Unix

This change maps the EOPNOTSUPP errno value (95) to std::io::ErrorKind::Unsupported in the decode_error_kind function for Unix platforms. Previously, it was incorrectly mapped to ErrorKind::Uncategorized.

Fixes #139803
---
 library/std/src/sys/pal/unix/mod.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs
index f8733eb611986..3a790d9c868c9 100644
--- a/library/std/src/sys/pal/unix/mod.rs
+++ b/library/std/src/sys/pal/unix/mod.rs
@@ -274,6 +274,7 @@ pub fn decode_error_kind(errno: i32) -> ErrorKind {
         libc::ETXTBSY => ExecutableFileBusy,
         libc::EXDEV => CrossesDevices,
         libc::EINPROGRESS => InProgress,
+        libc::EOPNOTSUPP => Unsupported,
 
         libc::EACCES | libc::EPERM => PermissionDenied,
 

From cb22c1d5e949b64aafb99994befde4bd25a421e9 Mon Sep 17 00:00:00 2001
From: Folkert de Vries <folkert@folkertdev.nl>
Date: Mon, 14 Apr 2025 14:36:53 +0200
Subject: [PATCH 20/24] Allow (but don't require) `#[unsafe(naked)]` so that
 `compiler-builtins` can upgrade to it

---
 compiler/rustc_parse/src/validate_attr.rs |  6 +++
 tests/ui/asm/naked-functions.rs           | 56 +++++++++++------------
 2 files changed, 34 insertions(+), 28 deletions(-)

diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_parse/src/validate_attr.rs
index 6a1c2af48ed50..b518fca7a6583 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_parse/src/validate_attr.rs
@@ -194,6 +194,12 @@ pub fn check_attribute_safety(psess: &ParseSess, safety: AttributeSafety, attr:
             }
         }
     } else if let Safety::Unsafe(unsafe_span) = attr_item.unsafety {
+        // Allow (but don't require) `#[unsafe(naked)]` so that compiler-builtins can upgrade to it.
+        // FIXME(#139797): remove this special case when compiler-builtins has upgraded.
+        if attr.has_name(sym::naked) {
+            return;
+        }
+
         psess.dcx().emit_err(errors::InvalidAttrUnsafe {
             span: unsafe_span,
             name: attr_item.path.clone(),
diff --git a/tests/ui/asm/naked-functions.rs b/tests/ui/asm/naked-functions.rs
index 5bf2e2a3abd06..8ba0eecb7b5c7 100644
--- a/tests/ui/asm/naked-functions.rs
+++ b/tests/ui/asm/naked-functions.rs
@@ -8,7 +8,7 @@
 
 use std::arch::{asm, naked_asm};
 
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn inline_asm_macro() {
     asm!("", options(raw));
     //~^ERROR the `asm!` macro is not allowed in naked functions
@@ -20,7 +20,7 @@ pub struct P {
     y: u16,
 }
 
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn patterns(
     mut a: u32,
     //~^ ERROR patterns not allowed in naked function parameters
@@ -34,27 +34,27 @@ pub unsafe extern "C" fn patterns(
     naked_asm!("")
 }
 
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn inc(a: u32) -> u32 {
     //~^ ERROR naked functions must contain a single `naked_asm!` invocation
     a + 1
     //~^ ERROR referencing function parameters is not allowed in naked functions
 }
 
-#[naked]
+#[unsafe(naked)]
 #[allow(asm_sub_register)]
 pub unsafe extern "C" fn inc_asm(a: u32) -> u32 {
     naked_asm!("/* {0} */", in(reg) a)
     //~^ ERROR the `in` operand cannot be used with `naked_asm!`
 }
 
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn inc_closure(a: u32) -> u32 {
     //~^ ERROR naked functions must contain a single `naked_asm!` invocation
     (|| a + 1)()
 }
 
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn unsupported_operands() {
     //~^ ERROR naked functions must contain a single `naked_asm!` invocation
     let mut a = 0usize;
@@ -76,12 +76,12 @@ pub unsafe extern "C" fn unsupported_operands() {
     );
 }
 
-#[naked]
+#[unsafe(naked)]
 pub extern "C" fn missing_assembly() {
     //~^ ERROR naked functions must contain a single `naked_asm!` invocation
 }
 
-#[naked]
+#[unsafe(naked)]
 pub extern "C" fn too_many_asm_blocks() {
     //~^ ERROR naked functions must contain a single `naked_asm!` invocation
     unsafe {
@@ -92,7 +92,7 @@ pub extern "C" fn too_many_asm_blocks() {
 }
 
 pub fn outer(x: u32) -> extern "C" fn(usize) -> usize {
-    #[naked]
+    #[unsafe(naked)]
     pub extern "C" fn inner(y: usize) -> usize {
         //~^ ERROR naked functions must contain a single `naked_asm!` invocation
         *&y
@@ -101,14 +101,14 @@ pub fn outer(x: u32) -> extern "C" fn(usize) -> usize {
     inner
 }
 
-#[naked]
+#[unsafe(naked)]
 unsafe extern "C" fn invalid_options() {
     naked_asm!("", options(nomem, preserves_flags));
     //~^ ERROR the `nomem` option cannot be used with `naked_asm!`
     //~| ERROR the `preserves_flags` option cannot be used with `naked_asm!`
 }
 
-#[naked]
+#[unsafe(naked)]
 unsafe extern "C" fn invalid_options_continued() {
     naked_asm!("", options(readonly, nostack), options(pure));
     //~^ ERROR the `readonly` option cannot be used with `naked_asm!`
@@ -116,20 +116,20 @@ unsafe extern "C" fn invalid_options_continued() {
     //~| ERROR the `pure` option cannot be used with `naked_asm!`
 }
 
-#[naked]
+#[unsafe(naked)]
 unsafe extern "C" fn invalid_may_unwind() {
     naked_asm!("", options(may_unwind));
     //~^ ERROR the `may_unwind` option cannot be used with `naked_asm!`
 }
 
-#[naked]
+#[unsafe(naked)]
 pub extern "C" fn valid_a<T>() -> T {
     unsafe {
         naked_asm!("");
     }
 }
 
-#[naked]
+#[unsafe(naked)]
 pub extern "C" fn valid_b() {
     unsafe {
         {
@@ -140,32 +140,32 @@ pub extern "C" fn valid_b() {
     }
 }
 
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn valid_c() {
     naked_asm!("");
 }
 
 #[cfg(target_arch = "x86_64")]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn valid_att_syntax() {
     naked_asm!("", options(att_syntax));
 }
 
-#[naked]
-#[naked]
+#[unsafe(naked)]
+#[unsafe(naked)]
 pub unsafe extern "C" fn allow_compile_error(a: u32) -> u32 {
     compile_error!("this is a user specified error")
     //~^ ERROR this is a user specified error
 }
 
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn allow_compile_error_and_asm(a: u32) -> u32 {
     compile_error!("this is a user specified error");
     //~^ ERROR this is a user specified error
     naked_asm!("")
 }
 
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn invalid_asm_syntax(a: u32) -> u32 {
     naked_asm!(invalid_syntax)
     //~^ ERROR asm template must be a string literal
@@ -173,7 +173,7 @@ pub unsafe extern "C" fn invalid_asm_syntax(a: u32) -> u32 {
 
 #[cfg(target_arch = "x86_64")]
 #[cfg_attr(target_pointer_width = "64", no_mangle)]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn compatible_cfg_attributes() {
     naked_asm!("", options(att_syntax));
 }
@@ -182,20 +182,20 @@ pub unsafe extern "C" fn compatible_cfg_attributes() {
 #[warn(dead_code)]
 #[deny(dead_code)]
 #[forbid(dead_code)]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn compatible_diagnostic_attributes() {
     naked_asm!("", options(raw));
 }
 
 #[deprecated = "test"]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn compatible_deprecated_attributes() {
     naked_asm!("", options(raw));
 }
 
 #[cfg(target_arch = "x86_64")]
 #[must_use]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn compatible_must_use_attributes() -> u64 {
     naked_asm!(
         "
@@ -207,13 +207,13 @@ pub unsafe extern "C" fn compatible_must_use_attributes() -> u64 {
 
 #[export_name = "exported_function_name"]
 #[link_section = ".custom_section"]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn compatible_ffi_attributes_1() {
     naked_asm!("", options(raw));
 }
 
 #[cold]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn compatible_codegen_attributes() {
     naked_asm!("", options(raw));
 }
@@ -222,13 +222,13 @@ pub unsafe extern "C" fn compatible_codegen_attributes() {
 /// a doc comment
 // a normal comment
 #[doc(alias = "ADocAlias")]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn compatible_doc_attributes() {
     naked_asm!("", options(raw));
 }
 
 #[linkage = "external"]
-#[naked]
+#[unsafe(naked)]
 pub unsafe extern "C" fn compatible_linkage() {
     naked_asm!("", options(raw));
 }

From b26f3d4347ca589305a19d10c6e651b071849716 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Fri, 11 Apr 2025 16:50:20 +1000
Subject: [PATCH 21/24] Move `opt_rpitit_info` field to `hir::AssocKind::Type`.

From `hir::AssocItem`.
---
 .../rustc_hir_analysis/src/check/check.rs     |  6 ++--
 .../src/check/compare_impl_item.rs            | 19 ++++++-----
 compiler/rustc_hir_analysis/src/check/mod.rs  |  2 +-
 .../rustc_hir_analysis/src/check/wfcheck.rs   |  6 ++--
 .../src/collect/type_of/opaque.rs             |  2 +-
 .../errors/wrong_number_of_generic_args.rs    |  4 +--
 .../src/hir_ty_lowering/dyn_compatibility.rs  |  2 +-
 .../src/hir_ty_lowering/mod.rs                |  2 +-
 .../rustc_hir_analysis/src/impl_wf_check.rs   |  2 +-
 compiler/rustc_hir_typeck/src/method/probe.rs | 12 ++-----
 compiler/rustc_metadata/src/rmeta/decoder.rs  | 12 ++++---
 compiler/rustc_metadata/src/rmeta/encoder.rs  |  4 +--
 compiler/rustc_middle/src/ty/assoc.rs         | 34 +++++++++++--------
 compiler/rustc_middle/src/ty/context.rs       |  2 +-
 compiler/rustc_middle/src/ty/mod.rs           |  6 ++--
 compiler/rustc_middle/src/ty/sty.rs           |  2 +-
 .../cfi/typeid/itanium_cxx_abi/transform.rs   |  2 +-
 .../rustc_smir/src/rustc_smir/convert/ty.rs   |  7 ++--
 .../rustc_smir/src/stable_mir/mir/pretty.rs   |  2 +-
 compiler/rustc_smir/src/stable_mir/ty.rs      | 18 +++++-----
 .../src/error_reporting/infer/mod.rs          |  8 +++--
 .../src/error_reporting/traits/ambiguity.rs   |  2 +-
 .../src/error_reporting/traits/suggestions.rs |  2 +-
 .../src/traits/dyn_compatibility.rs           |  4 +--
 .../src/traits/select/confirmation.rs         |  4 +--
 compiler/rustc_ty_utils/src/assoc.rs          | 24 +++++++------
 src/librustdoc/clean/mod.rs                   |  2 +-
 .../src/implied_bounds_in_impls.rs            |  2 +-
 28 files changed, 103 insertions(+), 91 deletions(-)

diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index c2706a1d4013e..12c36e0f4c265 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -449,7 +449,7 @@ fn best_definition_site_of_opaque<'tcx>(
                             return Some(span);
                         }
                     }
-                    ty::AssocKind::Type => {}
+                    ty::AssocKind::Type { .. } => {}
                 }
             }
 
@@ -740,7 +740,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
             for &assoc_item in assoc_items.in_definition_order() {
                 match assoc_item.kind {
-                    ty::AssocKind::Type if assoc_item.defaultness(tcx).has_value() => {
+                    ty::AssocKind::Type { .. } if assoc_item.defaultness(tcx).has_value() => {
                         let trait_args = GenericArgs::identity_for_item(tcx, def_id);
                         let _: Result<_, rustc_errors::ErrorGuaranteed> = check_type_bounds(
                             tcx,
@@ -953,7 +953,7 @@ fn check_impl_items_against_trait<'tcx>(
                     );
                 }
                 ty::AssocKind::Const => {}
-                ty::AssocKind::Type => {}
+                ty::AssocKind::Type { .. } => {}
             }
         }
 
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 7dfdf1ae237d9..d208aa71971e0 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -44,7 +44,7 @@ pub(super) fn compare_impl_item(
 
     match impl_item.kind {
         ty::AssocKind::Fn { .. } => compare_impl_method(tcx, impl_item, trait_item, impl_trait_ref),
-        ty::AssocKind::Type => compare_impl_ty(tcx, impl_item, trait_item, impl_trait_ref),
+        ty::AssocKind::Type { .. } => compare_impl_ty(tcx, impl_item, trait_item, impl_trait_ref),
         ty::AssocKind::Const => compare_impl_const(tcx, impl_item, trait_item, impl_trait_ref),
     }
 }
@@ -1703,7 +1703,7 @@ fn compare_generic_param_kinds<'tcx>(
     trait_item: ty::AssocItem,
     delay: bool,
 ) -> Result<(), ErrorGuaranteed> {
-    assert_eq!(impl_item.kind, trait_item.kind);
+    assert_eq!(impl_item.as_tag(), trait_item.as_tag());
 
     let ty_const_params_of = |def_id| {
         tcx.generics_of(def_id).own_params.iter().filter(|param| {
@@ -2235,16 +2235,19 @@ fn param_env_with_gat_bounds<'tcx>(
     // of the RPITITs associated with the same body. This is because checking
     // the item bounds of RPITITs often involves nested RPITITs having to prove
     // bounds about themselves.
-    let impl_tys_to_install = match impl_ty.opt_rpitit_info {
-        None => vec![impl_ty],
-        Some(
-            ty::ImplTraitInTraitData::Impl { fn_def_id }
-            | ty::ImplTraitInTraitData::Trait { fn_def_id, .. },
-        ) => tcx
+    let impl_tys_to_install = match impl_ty.kind {
+        ty::AssocKind::Type {
+            opt_rpitit_info:
+                Some(
+                    ty::ImplTraitInTraitData::Impl { fn_def_id }
+                    | ty::ImplTraitInTraitData::Trait { fn_def_id, .. },
+                ),
+        } => tcx
             .associated_types_for_impl_traits_in_associated_fn(fn_def_id)
             .iter()
             .map(|def_id| tcx.associated_item(*def_id))
             .collect(),
+        _ => vec![impl_ty],
     };
 
     for impl_ty in impl_tys_to_install {
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index 523db9440a41e..ec934b1f620dd 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -499,7 +499,7 @@ fn suggestion_signature<'tcx>(
             tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args),
             assoc,
         ),
-        ty::AssocKind::Type => {
+        ty::AssocKind::Type { .. } => {
             let (generics, where_clauses) = bounds_from_generic_predicates(
                 tcx,
                 tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args),
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index af7830fd6642a..c6c370c4a8467 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -408,7 +408,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
             let gat_def_id = gat_item.def_id.expect_local();
             let gat_item = tcx.associated_item(gat_def_id);
             // If this item is not an assoc ty, or has no args, then it's not a GAT
-            if gat_item.kind != ty::AssocKind::Type {
+            if !gat_item.is_type() {
                 continue;
             }
             let gat_generics = tcx.generics_of(gat_def_id);
@@ -453,7 +453,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
                         )
                     }
                     // In our example, this corresponds to the `Iter` and `Item` associated types
-                    ty::AssocKind::Type => {
+                    ty::AssocKind::Type { .. } => {
                         // If our associated item is a GAT with missing bounds, add them to
                         // the param-env here. This allows this GAT to propagate missing bounds
                         // to other GATs.
@@ -1101,7 +1101,7 @@ fn check_associated_item(
                 );
                 check_method_receiver(wfcx, hir_sig, item, self_ty)
             }
-            ty::AssocKind::Type => {
+            ty::AssocKind::Type { .. } => {
                 if let ty::AssocItemContainer::Trait = item.container {
                     check_associated_type_bounds(wfcx, item, span)
                 }
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index f06636447194a..653adc6b3ba5f 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -36,7 +36,7 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
                 locator.check(assoc_id.expect_local())
             }
             // Associated types don't have bodies, so they can't constrain hidden types
-            ty::AssocKind::Type => {}
+            ty::AssocKind::Type { .. } => {}
         }
     }
 
diff --git a/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs b/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
index 610b293a114e6..70d60bfcf2d20 100644
--- a/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
+++ b/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
@@ -4,7 +4,7 @@ use GenericArgsInfo::*;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, Diagnostic, EmissionGuarantee, MultiSpan, pluralize};
 use rustc_hir as hir;
-use rustc_middle::ty::{self as ty, AssocItems, AssocKind, TyCtxt};
+use rustc_middle::ty::{self as ty, AssocItems, TyCtxt};
 use rustc_span::def_id::DefId;
 use tracing::debug;
 
@@ -486,7 +486,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
             let items: &AssocItems = self.tcx.associated_items(self.def_id);
             items
                 .in_definition_order()
-                .filter(|item| item.kind == AssocKind::Type)
+                .filter(|item| item.is_type())
                 .filter(|item| {
                     !self
                         .gen_args
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
index e64cd8ec302c7..2e39beed8ae3c 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
@@ -201,7 +201,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                             tcx.associated_items(pred.trait_ref.def_id)
                                 .in_definition_order()
                                 // We only care about associated types.
-                                .filter(|item| item.kind == ty::AssocKind::Type)
+                                .filter(|item| item.is_type())
                                 // No RPITITs -- they're not dyn-compatible for now.
                                 .filter(|item| !item.is_impl_trait_in_trait())
                                 // If the associated type has a `where Self: Sized` bound,
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 0fb406d990803..0394dd20e28c8 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -1733,7 +1733,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         .any(|i| {
                             i.kind.namespace() == Namespace::TypeNS
                                 && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident
-                                && matches!(i.kind, ty::AssocKind::Type)
+                                && i.is_type()
                         })
                     // Consider only accessible traits
                     && tcx.visibility(*trait_def_id)
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check.rs b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
index 1ab36ce1dcb9e..127ca846b9fe0 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
@@ -112,7 +112,7 @@ pub(crate) fn enforce_impl_lifetime_params_are_constrained(
         .flat_map(|def_id| {
             let item = tcx.associated_item(def_id);
             match item.kind {
-                ty::AssocKind::Type => {
+                ty::AssocKind::Type { .. } => {
                     if item.defaultness(tcx).has_value() {
                         cgp::parameters_for(tcx, tcx.type_of(def_id).instantiate_identity(), true)
                     } else {
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index d5d85c812b2db..07cb8c2a5bbb5 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -1671,15 +1671,7 @@ impl<'tcx> Pick<'tcx> {
     /// Do not use for type checking.
     pub(crate) fn differs_from(&self, other: &Self) -> bool {
         let Self {
-            item:
-                AssocItem {
-                    def_id,
-                    name: _,
-                    kind: _,
-                    container: _,
-                    trait_item_def_id: _,
-                    opt_rpitit_info: _,
-                },
+            item: AssocItem { def_id, name: _, kind: _, container: _, trait_item_def_id: _ },
             kind: _,
             import_ids: _,
             autoderefs: _,
@@ -2253,7 +2245,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         match self.mode {
             Mode::MethodCall => item.is_method(),
             Mode::Path => match item.kind {
-                ty::AssocKind::Type => false,
+                ty::AssocKind::Type { .. } => false,
                 ty::AssocKind::Fn { .. } | ty::AssocKind::Const => true,
             },
         }
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index cc3b2a241e4ad..3cbe09280f690 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1342,12 +1342,17 @@ impl<'a> CrateMetadataRef<'a> {
             DefKind::AssocFn => {
                 ty::AssocKind::Fn { has_self: self.get_fn_has_self_parameter(id, sess) }
             }
-            DefKind::AssocTy => ty::AssocKind::Type,
+            DefKind::AssocTy => ty::AssocKind::Type {
+                opt_rpitit_info: self
+                    .root
+                    .tables
+                    .opt_rpitit_info
+                    .get(self, id)
+                    .map(|d| d.decode(self)),
+            },
             _ => bug!("cannot get associated-item of `{:?}`", self.def_key(id)),
         };
         let container = self.root.tables.assoc_container.get(self, id).unwrap();
-        let opt_rpitit_info =
-            self.root.tables.opt_rpitit_info.get(self, id).map(|d| d.decode(self));
 
         ty::AssocItem {
             name,
@@ -1355,7 +1360,6 @@ impl<'a> CrateMetadataRef<'a> {
             def_id: self.local_def_id(id),
             trait_item_def_id: self.get_trait_item_def_id(id),
             container,
-            opt_rpitit_info,
         }
     }
 
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index cc9da16ffdbb0..b900100c3c011 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1691,7 +1691,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
         match item.container {
             AssocItemContainer::Trait => {
-                if let ty::AssocKind::Type = item.kind {
+                if item.is_type() {
                     self.encode_explicit_item_bounds(def_id);
                     self.encode_explicit_item_self_bounds(def_id);
                     if tcx.is_conditionally_const(def_id) {
@@ -1706,7 +1706,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 }
             }
         }
-        if let Some(rpitit_info) = item.opt_rpitit_info {
+        if let ty::AssocKind::Type { opt_rpitit_info: Some(rpitit_info) } = item.kind {
             record!(self.tables.opt_rpitit_info[def_id] <- rpitit_info);
             if matches!(rpitit_info, ty::ImplTraitInTraitData::Trait { .. }) {
                 record_array!(
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index 3c1e5ed9e114d..eac8f04f84f9a 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -25,11 +25,6 @@ pub struct AssocItem {
     /// If this is an item in an impl of a trait then this is the `DefId` of
     /// the associated item on the trait that this implements.
     pub trait_item_def_id: Option<DefId>,
-
-    /// `Some` if the associated item (an associated type) comes from the
-    /// return-position `impl Trait` in trait desugaring. The `ImplTraitInTraitData`
-    /// provides additional information about its source.
-    pub opt_rpitit_info: Option<ty::ImplTraitInTraitData>,
 }
 
 impl AssocItem {
@@ -81,7 +76,7 @@ impl AssocItem {
                 // regions just fine, showing `fn(&MyType)`.
                 tcx.fn_sig(self.def_id).instantiate_identity().skip_binder().to_string()
             }
-            ty::AssocKind::Type => format!("type {};", self.name),
+            ty::AssocKind::Type { .. } => format!("type {};", self.name),
             ty::AssocKind::Const => {
                 format!(
                     "const {}: {:?};",
@@ -97,10 +92,14 @@ impl AssocItem {
             ty::AssocKind::Const => "associated const",
             ty::AssocKind::Fn { has_self: true } => "method",
             ty::AssocKind::Fn { has_self: false } => "associated function",
-            ty::AssocKind::Type => "associated type",
+            ty::AssocKind::Type { .. } => "associated type",
         }
     }
 
+    pub fn is_type(&self) -> bool {
+        matches!(self.kind, ty::AssocKind::Type { .. })
+    }
+
     pub fn is_fn(&self) -> bool {
         matches!(self.kind, ty::AssocKind::Fn { .. })
     }
@@ -113,12 +112,12 @@ impl AssocItem {
         match self.kind {
             AssocKind::Const => AssocTag::Const,
             AssocKind::Fn { .. } => AssocTag::Fn,
-            AssocKind::Type => AssocTag::Type,
+            AssocKind::Type { .. } => AssocTag::Type,
         }
     }
 
     pub fn is_impl_trait_in_trait(&self) -> bool {
-        self.opt_rpitit_info.is_some()
+        matches!(self.kind, AssocKind::Type { opt_rpitit_info: Some(_) })
     }
 
     /// Returns true if:
@@ -143,14 +142,21 @@ impl AssocItem {
 #[derive(Copy, Clone, PartialEq, Debug, HashStable, Eq, Hash, Encodable, Decodable)]
 pub enum AssocKind {
     Const,
-    Fn { has_self: bool },
-    Type,
+    Fn {
+        has_self: bool,
+    },
+    Type {
+        /// `Some` if the associated type comes from an RPITIT. The
+        /// `ImplTraitInTraitData` provides additional information about its
+        /// source.
+        opt_rpitit_info: Option<ty::ImplTraitInTraitData>,
+    },
 }
 
 impl AssocKind {
     pub fn namespace(&self) -> Namespace {
         match *self {
-            ty::AssocKind::Type => Namespace::TypeNS,
+            ty::AssocKind::Type { .. } => Namespace::TypeNS,
             ty::AssocKind::Const | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
         }
     }
@@ -159,7 +165,7 @@ impl AssocKind {
         match self {
             AssocKind::Const => DefKind::AssocConst,
             AssocKind::Fn { .. } => DefKind::AssocFn,
-            AssocKind::Type => DefKind::AssocTy,
+            AssocKind::Type { .. } => DefKind::AssocTy,
         }
     }
 }
@@ -170,7 +176,7 @@ impl std::fmt::Display for AssocKind {
             AssocKind::Fn { has_self: true } => write!(f, "method"),
             AssocKind::Fn { has_self: false } => write!(f, "associated function"),
             AssocKind::Const => write!(f, "associated const"),
-            AssocKind::Type => write!(f, "associated type"),
+            AssocKind::Type { .. } => write!(f, "associated type"),
         }
     }
 }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index abf6cbbcd8774..fb25b8e130b56 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -464,7 +464,7 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     fn associated_type_def_ids(self, def_id: DefId) -> impl IntoIterator<Item = DefId> {
         self.associated_items(def_id)
             .in_definition_order()
-            .filter(|assoc_item| matches!(assoc_item.kind, ty::AssocKind::Type))
+            .filter(|assoc_item| assoc_item.is_type())
             .map(|assoc_item| assoc_item.def_id)
     }
 
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 30c889c39d938..395d2ec48142c 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -1610,8 +1610,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// return-position `impl Trait` from a trait, then provide the source info
     /// about where that RPITIT came from.
     pub fn opt_rpitit_info(self, def_id: DefId) -> Option<ImplTraitInTraitData> {
-        if let DefKind::AssocTy = self.def_kind(def_id) {
-            self.associated_item(def_id).opt_rpitit_info
+        if let DefKind::AssocTy = self.def_kind(def_id)
+            && let AssocKind::Type { opt_rpitit_info } = self.associated_item(def_id).kind
+        {
+            opt_rpitit_info
         } else {
             None
         }
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 27ee363f1c142..bb178fe42538c 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -734,7 +734,7 @@ impl<'tcx> Ty<'tcx> {
                     .map(|principal| {
                         tcx.associated_items(principal.def_id())
                             .in_definition_order()
-                            .filter(|item| item.kind == ty::AssocKind::Type)
+                            .filter(|item| item.is_type())
                             .filter(|item| !item.is_impl_trait_in_trait())
                             .filter(|item| !tcx.generics_require_sized_self(item.def_id))
                             .count()
diff --git a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
index 718b9a4fa3b81..d2917478e4e43 100644
--- a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
+++ b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
@@ -240,7 +240,7 @@ fn trait_object_ty<'tcx>(tcx: TyCtxt<'tcx>, poly_trait_ref: ty::PolyTraitRef<'tc
         .flat_map(|super_poly_trait_ref| {
             tcx.associated_items(super_poly_trait_ref.def_id())
                 .in_definition_order()
-                .filter(|item| item.kind == ty::AssocKind::Type)
+                .filter(|item| item.is_type())
                 .filter(|item| !tcx.generics_require_sized_self(item.def_id))
                 .map(move |assoc_ty| {
                     super_poly_trait_ref.map_bound(|super_trait_ref| {
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
index 94f3be9fef734..55f698b8f211f 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
@@ -894,12 +894,14 @@ impl<'tcx> Stable<'tcx> for rustc_session::cstore::ForeignModule {
 impl<'tcx> Stable<'tcx> for ty::AssocKind {
     type T = stable_mir::ty::AssocKind;
 
-    fn stable(&self, _tables: &mut Tables<'_>) -> Self::T {
+    fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
         use stable_mir::ty::AssocKind;
         match *self {
             ty::AssocKind::Const => AssocKind::Const,
             ty::AssocKind::Fn { has_self } => AssocKind::Fn { has_self },
-            ty::AssocKind::Type => AssocKind::Type,
+            ty::AssocKind::Type { opt_rpitit_info } => AssocKind::Type {
+                opt_rpitit_info: opt_rpitit_info.map(|rpitit| rpitit.stable(tables)),
+            },
         }
     }
 }
@@ -926,7 +928,6 @@ impl<'tcx> Stable<'tcx> for ty::AssocItem {
             kind: self.kind.stable(tables),
             container: self.container.stable(tables),
             trait_item_def_id: self.trait_item_def_id.map(|did| tables.assoc_def(did)),
-            opt_rpitit_info: self.opt_rpitit_info.map(|rpitit| rpitit.stable(tables)),
         }
     }
 }
diff --git a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
index 60d9e122940bf..9fa97763907f1 100644
--- a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
+++ b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
@@ -25,7 +25,7 @@ impl Display for AssocKind {
             AssocKind::Fn { has_self: true } => write!(f, "method"),
             AssocKind::Fn { has_self: false } => write!(f, "associated function"),
             AssocKind::Const => write!(f, "associated const"),
-            AssocKind::Type => write!(f, "associated type"),
+            AssocKind::Type { .. } => write!(f, "associated type"),
         }
     }
 }
diff --git a/compiler/rustc_smir/src/stable_mir/ty.rs b/compiler/rustc_smir/src/stable_mir/ty.rs
index 63ce756162a52..6eac0885d7636 100644
--- a/compiler/rustc_smir/src/stable_mir/ty.rs
+++ b/compiler/rustc_smir/src/stable_mir/ty.rs
@@ -1585,18 +1585,20 @@ pub struct AssocItem {
     /// If this is an item in an impl of a trait then this is the `DefId` of
     /// the associated item on the trait that this implements.
     pub trait_item_def_id: Option<AssocDef>,
-
-    /// `Some` if the associated item (an associated type) comes from the
-    /// return-position `impl Trait` in trait desugaring. The `ImplTraitInTraitData`
-    /// provides additional information about its source.
-    pub opt_rpitit_info: Option<ImplTraitInTraitData>,
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 pub enum AssocKind {
     Const,
-    Fn { has_self: bool },
-    Type,
+    Fn {
+        has_self: bool,
+    },
+    Type {
+        /// `Some` if the associated type comes from an RPITIT. The
+        /// `ImplTraitInTraitData` provides additional information about its
+        /// source.
+        opt_rpitit_info: Option<ImplTraitInTraitData>,
+    },
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
@@ -1613,6 +1615,6 @@ pub enum ImplTraitInTraitData {
 
 impl AssocItem {
     pub fn is_impl_trait_in_trait(&self) -> bool {
-        self.opt_rpitit_info.is_some()
+        matches!(self.kind, AssocKind::Type { opt_rpitit_info: Some(_) })
     }
 }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
index cbadb46c17d94..1c71fe028d4d0 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -2337,7 +2337,7 @@ impl<'tcx> ObligationCause<'tcx> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 ObligationCauseFailureCode::MethodCompat { span, subdiags }
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type { .. }, .. } => {
                 ObligationCauseFailureCode::TypeCompat { span, subdiags }
             }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
@@ -2401,7 +2401,7 @@ impl<'tcx> ObligationCause<'tcx> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 "method type is compatible with trait"
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type { .. }, .. } => {
                 "associated type is compatible with trait"
             }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
@@ -2425,7 +2425,9 @@ impl IntoDiagArg for ObligationCauseAsDiagArg<'_> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 "method_compat"
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => "type_compat",
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type { .. }, .. } => {
+                "type_compat"
+            }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
                 "const_compat"
             }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
index e3e1583a48fac..c4b0ca9cf8fcc 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
@@ -352,7 +352,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             ty::AssocKind::Fn { .. } => ("call", "function"),
                             // This is already covered by E0223, but this following single match
                             // arm doesn't hurt here.
-                            ty::AssocKind::Type => ("refer to the", "type"),
+                            ty::AssocKind::Type { .. } => ("refer to the", "type"),
                         };
 
                         // Replace the more general E0283 with a more specific error
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index 38aac8e70b529..084942cd8afd4 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2112,7 +2112,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         trait_ref: DefId,
     ) {
         if let Some(assoc_item) = self.tcx.opt_associated_item(item_def_id) {
-            if let ty::AssocKind::Const | ty::AssocKind::Type = assoc_item.kind {
+            if let ty::AssocKind::Const | ty::AssocKind::Type { .. } = assoc_item.kind {
                 err.note(format!(
                     "{}s cannot be accessed directly on a `trait`, they can only be \
                         accessed through a specific `impl`",
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index 76892db9ef7b4..1ef16f34702ea 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -188,7 +188,7 @@ fn bounds_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId) -> SmallVec<[Span
     tcx.associated_items(trait_def_id)
         .in_definition_order()
         // We're only looking at associated type bounds
-        .filter(|item| item.kind == ty::AssocKind::Type)
+        .filter(|item| item.is_type())
         // Ignore GATs with `Self: Sized`
         .filter(|item| !tcx.generics_require_sized_self(item.def_id))
         .flat_map(|item| tcx.explicit_item_bounds(item.def_id).iter_identity_copied())
@@ -320,7 +320,7 @@ pub fn dyn_compatibility_violations_for_assoc_item(
             })
             .collect(),
         // Associated types can only be dyn-compatible if they have `Self: Sized` bounds.
-        ty::AssocKind::Type => {
+        ty::AssocKind::Type { .. } => {
             if !tcx.generics_of(item.def_id).is_own_empty() && !item.is_impl_trait_in_trait() {
                 vec![DynCompatibilityViolation::GAT(item.name, item.ident(tcx).span)]
             } else {
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 69e7b2a43ff9b..d71d1e9ae0faf 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -594,9 +594,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // Associated types that require `Self: Sized` do not show up in the built-in
             // implementation of `Trait for dyn Trait`, and can be dropped here.
             .filter(|item| !tcx.generics_require_sized_self(item.def_id))
-            .filter_map(
-                |item| if item.kind == ty::AssocKind::Type { Some(item.def_id) } else { None },
-            )
+            .filter_map(|item| if item.is_type() { Some(item.def_id) } else { None })
             .collect();
 
         for assoc_type in assoc_types {
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index 79de071b6878e..2275fbb97923b 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -132,7 +132,7 @@ fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty
     let kind = match trait_item_ref.kind {
         hir::AssocItemKind::Const => ty::AssocKind::Const,
         hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { has_self },
-        hir::AssocItemKind::Type => ty::AssocKind::Type,
+        hir::AssocItemKind::Type => ty::AssocKind::Type { opt_rpitit_info: None },
     };
 
     ty::AssocItem {
@@ -141,7 +141,6 @@ fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty
         def_id: owner_id.to_def_id(),
         trait_item_def_id: Some(owner_id.to_def_id()),
         container: ty::AssocItemContainer::Trait,
-        opt_rpitit_info: None,
     }
 }
 
@@ -150,7 +149,7 @@ fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::A
     let kind = match impl_item_ref.kind {
         hir::AssocItemKind::Const => ty::AssocKind::Const,
         hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { has_self },
-        hir::AssocItemKind::Type => ty::AssocKind::Type,
+        hir::AssocItemKind::Type => ty::AssocKind::Type { opt_rpitit_info: None },
     };
 
     ty::AssocItem {
@@ -159,7 +158,6 @@ fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::A
         def_id: def_id.to_def_id(),
         trait_item_def_id: impl_item_ref.trait_item_def_id,
         container: ty::AssocItemContainer::Impl,
-        opt_rpitit_info: None,
     }
 }
 
@@ -263,14 +261,15 @@ fn associated_type_for_impl_trait_in_trait(
 
     trait_assoc_ty.associated_item(ty::AssocItem {
         name: kw::Empty,
-        kind: ty::AssocKind::Type,
+        kind: ty::AssocKind::Type {
+            opt_rpitit_info: Some(ImplTraitInTraitData::Trait {
+                fn_def_id: fn_def_id.to_def_id(),
+                opaque_def_id: opaque_ty_def_id.to_def_id(),
+            }),
+        },
         def_id,
         trait_item_def_id: None,
         container: ty::AssocItemContainer::Trait,
-        opt_rpitit_info: Some(ImplTraitInTraitData::Trait {
-            fn_def_id: fn_def_id.to_def_id(),
-            opaque_def_id: opaque_ty_def_id.to_def_id(),
-        }),
     });
 
     // Copy visility of the containing function.
@@ -315,11 +314,14 @@ fn associated_type_for_impl_trait_in_impl(
 
     impl_assoc_ty.associated_item(ty::AssocItem {
         name: kw::Empty,
-        kind: ty::AssocKind::Type,
+        kind: ty::AssocKind::Type {
+            opt_rpitit_info: Some(ImplTraitInTraitData::Impl {
+                fn_def_id: impl_fn_def_id.to_def_id(),
+            }),
+        },
         def_id,
         trait_item_def_id: Some(trait_assoc_def_id),
         container: ty::AssocItemContainer::Impl,
-        opt_rpitit_info: Some(ImplTraitInTraitData::Impl { fn_def_id: impl_fn_def_id.to_def_id() }),
     });
 
     // Copy visility of the containing function.
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 7cfd204aa1375..74dbc7d06001d 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1412,7 +1412,7 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
                 RequiredMethodItem(item)
             }
         }
-        ty::AssocKind::Type => {
+        ty::AssocKind::Type { .. } => {
             let my_name = assoc_item.name;
 
             fn param_eq_arg(param: &GenericParamDef, arg: &GenericArg) -> bool {
diff --git a/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs b/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
index d02d9b2102bda..430f24111832c 100644
--- a/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
+++ b/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
@@ -315,7 +315,7 @@ fn check<'tcx>(cx: &LateContext<'tcx>, bounds: GenericBounds<'tcx>) {
                 assocs
                     .filter_by_name_unhygienic(constraint.ident.name)
                     .next()
-                    .is_some_and(|assoc| assoc.kind == ty::AssocKind::Type)
+                    .is_some_and(|assoc| assoc.is_type())
                 })
         {
             emit_lint(cx, poly_trait, bounds, index, implied_constraints, bound);

From 89e93a51c81b521a9601b365e3325d31e44e9198 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Mon, 14 Apr 2025 15:39:47 +1000
Subject: [PATCH 22/24] Move two methods from `AssocKind` to `AssocItem`.

Because all the other similar methods are on `AssocItem`.
---
 .../src/coherence/inherent_impls_overlap.rs   |  2 +-
 .../src/hir_ty_lowering/lint.rs               |  2 +-
 .../src/hir_ty_lowering/mod.rs                |  2 +-
 compiler/rustc_hir_typeck/src/method/mod.rs   |  2 +-
 compiler/rustc_hir_typeck/src/method/probe.rs |  4 +--
 .../rustc_hir_typeck/src/method/suggest.rs    |  4 +--
 compiler/rustc_middle/src/ty/assoc.rs         | 33 +++++++++----------
 .../src/error_reporting/traits/suggestions.rs |  2 +-
 .../passes/collect_intra_doc_links.rs         |  4 +--
 9 files changed, 26 insertions(+), 29 deletions(-)

diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
index dc616576c9c1b..cbfad1f6883e5 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
@@ -64,7 +64,7 @@ impl<'tcx> InherentOverlapChecker<'tcx> {
 
     fn compare_hygienically(&self, item1: ty::AssocItem, item2: ty::AssocItem) -> bool {
         // Symbols and namespace match, compare hygienically.
-        item1.kind.namespace() == item2.kind.namespace()
+        item1.namespace() == item2.namespace()
             && item1.ident(self.tcx).normalize_to_macros_2_0()
                 == item2.ident(self.tcx).normalize_to_macros_2_0()
     }
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
index 8e62dce21913b..49fd55b03a255 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
@@ -501,7 +501,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let names: Vec<_> = tcx
             .associated_items(trait_def_id)
             .in_definition_order()
-            .filter(|assoc| assoc.kind.namespace() == Namespace::ValueNS)
+            .filter(|assoc| assoc.namespace() == Namespace::ValueNS)
             .map(|cand| cand.name)
             .collect();
         if let Some(typo) = find_best_match_for_name(&names, segment.ident.name, None) {
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 0394dd20e28c8..7605c6c6a420a 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -1731,7 +1731,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 tcx.associated_items(*trait_def_id)
                         .in_definition_order()
                         .any(|i| {
-                            i.kind.namespace() == Namespace::TypeNS
+                            i.namespace() == Namespace::TypeNS
                                 && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident
                                 && i.is_type()
                         })
diff --git a/compiler/rustc_hir_typeck/src/method/mod.rs b/compiler/rustc_hir_typeck/src/method/mod.rs
index 39cb139a199ed..1b67e2306aa74 100644
--- a/compiler/rustc_hir_typeck/src/method/mod.rs
+++ b/compiler/rustc_hir_typeck/src/method/mod.rs
@@ -529,7 +529,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
-        let def_kind = pick.item.kind.as_def_kind();
+        let def_kind = pick.item.as_def_kind();
         tcx.check_stability(pick.item.def_id, Some(expr_id), span, Some(method_name.span));
         Ok((def_kind, pick.item.def_id))
     }
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 07cb8c2a5bbb5..c14b7823e3703 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -1583,7 +1583,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 },
                 None,
             ) {
-                self.private_candidate.set(Some((pick.item.kind.as_def_kind(), pick.item.def_id)));
+                self.private_candidate.set(Some((pick.item.as_def_kind(), pick.item.def_id)));
             }
         }
         None
@@ -1694,7 +1694,7 @@ impl<'tcx> Pick<'tcx> {
         if self.unstable_candidates.is_empty() {
             return;
         }
-        let def_kind = self.item.kind.as_def_kind();
+        let def_kind = self.item.as_def_kind();
         tcx.node_span_lint(lint::builtin::UNSTABLE_NAME_COLLISIONS, scope_expr_id, span, |lint| {
             lint.primary_message(format!(
                 "{} {} with this name may be added to the standard library in the future",
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 1b9771636a7d8..962871ed2d112 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -1819,7 +1819,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         mode: Mode,
     ) {
         let tcx = self.tcx;
-        let def_kind = similar_candidate.kind.as_def_kind();
+        let def_kind = similar_candidate.as_def_kind();
         let an = self.tcx.def_kind_descr_article(def_kind, similar_candidate.def_id);
         let msg = format!(
             "there is {an} {} `{}` with a similar name",
@@ -4288,7 +4288,7 @@ fn print_disambiguation_help<'tcx>(
             && let SelfSource::MethodCall(receiver) = source
             && let Some(args) = args
         {
-            let def_kind_descr = tcx.def_kind_descr(item.kind.as_def_kind(), item.def_id);
+            let def_kind_descr = tcx.def_kind_descr(item.as_def_kind(), item.def_id);
             let item_name = item.ident(tcx);
             let first_input =
                 tcx.fn_sig(item.def_id).instantiate_identity().skip_binder().inputs().get(0);
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index eac8f04f84f9a..6138157d83626 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -96,6 +96,20 @@ impl AssocItem {
         }
     }
 
+    pub fn namespace(&self) -> Namespace {
+        match self.kind {
+            ty::AssocKind::Type { .. } => Namespace::TypeNS,
+            ty::AssocKind::Const | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
+        }
+    }
+
+    pub fn as_def_kind(&self) -> DefKind {
+        match self.kind {
+            AssocKind::Const => DefKind::AssocConst,
+            AssocKind::Fn { .. } => DefKind::AssocFn,
+            AssocKind::Type { .. } => DefKind::AssocTy,
+        }
+    }
     pub fn is_type(&self) -> bool {
         matches!(self.kind, ty::AssocKind::Type { .. })
     }
@@ -153,23 +167,6 @@ pub enum AssocKind {
     },
 }
 
-impl AssocKind {
-    pub fn namespace(&self) -> Namespace {
-        match *self {
-            ty::AssocKind::Type { .. } => Namespace::TypeNS,
-            ty::AssocKind::Const | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
-        }
-    }
-
-    pub fn as_def_kind(&self) -> DefKind {
-        match self {
-            AssocKind::Const => DefKind::AssocConst,
-            AssocKind::Fn { .. } => DefKind::AssocFn,
-            AssocKind::Type { .. } => DefKind::AssocTy,
-        }
-    }
-}
-
 impl std::fmt::Display for AssocKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
@@ -250,7 +247,7 @@ impl AssocItems {
         parent_def_id: DefId,
     ) -> Option<&ty::AssocItem> {
         self.filter_by_name_unhygienic(ident.name)
-            .filter(|item| item.kind.namespace() == ns)
+            .filter(|item| item.namespace() == ns)
             .find(|item| tcx.hygienic_eq(ident, item.ident(tcx), parent_def_id))
     }
 }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index 084942cd8afd4..08b95b450583b 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2116,7 +2116,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 err.note(format!(
                     "{}s cannot be accessed directly on a `trait`, they can only be \
                         accessed through a specific `impl`",
-                    self.tcx.def_kind_descr(assoc_item.kind.as_def_kind(), item_def_id)
+                    self.tcx.def_kind_descr(assoc_item.as_def_kind(), item_def_id)
                 ));
                 err.span_suggestion(
                     span,
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index fdbb792d25dab..297597b3deacc 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -60,7 +60,7 @@ fn filter_assoc_items_by_name_and_namespace(
     ns: Namespace,
 ) -> impl Iterator<Item = &ty::AssocItem> {
     tcx.associated_items(assoc_items_of).filter_by_name_unhygienic(ident.name).filter(move |item| {
-        item.kind.namespace() == ns && tcx.hygienic_eq(ident, item.ident(tcx), assoc_items_of)
+        item.namespace() == ns && tcx.hygienic_eq(ident, item.ident(tcx), assoc_items_of)
     })
 }
 
@@ -743,7 +743,7 @@ impl<'tcx> LinkCollector<'_, 'tcx> {
                 ns,
             )
             .map(|item| {
-                let res = Res::Def(item.kind.as_def_kind(), item.def_id);
+                let res = Res::Def(item.as_def_kind(), item.def_id);
                 (res, item.def_id)
             })
             .collect::<Vec<_>>(),

From 78599d83e7ab9f8cd4cbb9e982ddf12f258d6b18 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Mon, 14 Apr 2025 13:15:01 +1000
Subject: [PATCH 23/24] Move `name` field from `AssocItem` to `AssocKind`
 variants.

To accurately reflect that RPITIT assoc items don't have a name. This
avoids the use of `kw::Empty` to mean "no name", which is error prone.

Helps with #137978.
---
 .../rustc_hir_analysis/src/check/check.rs     |   4 +-
 .../src/check/compare_impl_item.rs            |  32 +++---
 compiler/rustc_hir_analysis/src/check/mod.rs  |  10 +-
 .../rustc_hir_analysis/src/check/wfcheck.rs   |   4 +-
 .../src/coherence/inherent_impls_overlap.rs   |   8 +-
 .../src/collect/type_of/opaque.rs             |   2 +-
 .../errors/wrong_number_of_generic_args.rs    |   2 +-
 .../src/hir_ty_lowering/errors.rs             |  38 ++++---
 .../src/hir_ty_lowering/lint.rs               |   2 +-
 .../rustc_hir_analysis/src/impl_wf_check.rs   |   2 +-
 compiler/rustc_hir_typeck/src/expr.rs         |   5 +-
 .../rustc_hir_typeck/src/fn_ctxt/checks.rs    |   9 +-
 .../src/fn_ctxt/suggestions.rs                |  11 +-
 compiler/rustc_hir_typeck/src/lib.rs          |   2 +-
 compiler/rustc_hir_typeck/src/method/probe.rs |  25 ++---
 .../rustc_hir_typeck/src/method/suggest.rs    |  27 +++--
 compiler/rustc_hir_typeck/src/op.rs           |   2 +-
 compiler/rustc_metadata/src/rmeta/decoder.rs  |  30 +++---
 compiler/rustc_metadata/src/rmeta/encoder.rs  |   2 +-
 compiler/rustc_middle/src/ty/assoc.rs         | 101 ++++++++++++------
 compiler/rustc_middle/src/ty/mod.rs           |   5 +-
 compiler/rustc_middle/src/ty/print/pretty.rs  |   6 +-
 .../src/check_undefined_transmutes.rs         |   2 +-
 .../rustc_resolve/src/late/diagnostics.rs     |   5 +-
 .../rustc_smir/src/rustc_smir/convert/ty.rs   |  18 ++--
 .../rustc_smir/src/stable_mir/mir/pretty.rs   |   6 +-
 compiler/rustc_smir/src/stable_mir/ty.rs      |  25 ++---
 compiler/rustc_symbol_mangling/src/v0.rs      |   2 +-
 .../src/error_reporting/infer/mod.rs          |   6 +-
 .../error_reporting/infer/note_and_explain.rs |   2 +-
 .../src/error_reporting/infer/region.rs       |   2 +-
 .../src/error_reporting/traits/ambiguity.rs   |   2 +-
 .../src/error_reporting/traits/suggestions.rs |   8 +-
 .../src/traits/dyn_compatibility.rs           |  42 ++++----
 .../src/traits/project.rs                     |   9 +-
 compiler/rustc_ty_utils/src/assoc.rs          |  23 ++--
 src/librustdoc/clean/mod.rs                   |  12 +--
 src/librustdoc/clean/types.rs                 |   2 +-
 .../clippy_lints/src/assigning_clones.rs      |   4 +-
 .../src/methods/double_ended_iterator_last.rs |   2 +-
 .../clippy_lints/src/missing_trait_methods.rs |   2 +-
 .../clippy_lints/src/same_name_method.rs      |   2 +-
 .../src/unconditional_recursion.rs            |   2 +-
 43 files changed, 276 insertions(+), 231 deletions(-)

diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 12c36e0f4c265..4f338c6a19e69 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -443,7 +443,7 @@ fn best_definition_site_of_opaque<'tcx>(
             let impl_def_id = tcx.local_parent(parent);
             for assoc in tcx.associated_items(impl_def_id).in_definition_order() {
                 match assoc.kind {
-                    ty::AssocKind::Const | ty::AssocKind::Fn { .. } => {
+                    ty::AssocKind::Const { .. } | ty::AssocKind::Fn { .. } => {
                         if let ControlFlow::Break(span) = locator.check(assoc.def_id.expect_local())
                         {
                             return Some(span);
@@ -952,7 +952,7 @@ fn check_impl_items_against_trait<'tcx>(
                             .instantiate_identity(),
                     );
                 }
-                ty::AssocKind::Const => {}
+                ty::AssocKind::Const { .. } => {}
                 ty::AssocKind::Type { .. } => {}
             }
         }
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index d208aa71971e0..af26d2ee00caf 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -45,7 +45,9 @@ pub(super) fn compare_impl_item(
     match impl_item.kind {
         ty::AssocKind::Fn { .. } => compare_impl_method(tcx, impl_item, trait_item, impl_trait_ref),
         ty::AssocKind::Type { .. } => compare_impl_ty(tcx, impl_item, trait_item, impl_trait_ref),
-        ty::AssocKind::Const => compare_impl_const(tcx, impl_item, trait_item, impl_trait_ref),
+        ty::AssocKind::Const { .. } => {
+            compare_impl_const(tcx, impl_item, trait_item, impl_trait_ref)
+        }
     }
 }
 
@@ -654,7 +656,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
                 cause.span,
                 E0053,
                 "method `{}` has an incompatible return type for trait",
-                trait_m.name
+                trait_m.name()
             );
             infcx.err_ctxt().note_type_err(
                 &mut diag,
@@ -1032,7 +1034,7 @@ fn report_trait_method_mismatch<'tcx>(
         impl_err_span,
         E0053,
         "method `{}` has an incompatible type for trait",
-        trait_m.name
+        trait_m.name()
     );
     match &terr {
         TypeError::ArgumentMutability(0) | TypeError::ArgumentSorts(_, 0)
@@ -1266,14 +1268,14 @@ fn compare_self_type<'tcx>(
                 impl_m_span,
                 E0185,
                 "method `{}` has a `{}` declaration in the impl, but not in the trait",
-                trait_m.name,
+                trait_m.name(),
                 self_descr
             );
             err.span_label(impl_m_span, format!("`{self_descr}` used in impl"));
             if let Some(span) = tcx.hir_span_if_local(trait_m.def_id) {
                 err.span_label(span, format!("trait method declared without `{self_descr}`"));
             } else {
-                err.note_trait_signature(trait_m.name, trait_m.signature(tcx));
+                err.note_trait_signature(trait_m.name(), trait_m.signature(tcx));
             }
             return Err(err.emit_unless(delay));
         }
@@ -1286,14 +1288,14 @@ fn compare_self_type<'tcx>(
                 impl_m_span,
                 E0186,
                 "method `{}` has a `{}` declaration in the trait, but not in the impl",
-                trait_m.name,
+                trait_m.name(),
                 self_descr
             );
             err.span_label(impl_m_span, format!("expected `{self_descr}` in impl"));
             if let Some(span) = tcx.hir_span_if_local(trait_m.def_id) {
                 err.span_label(span, format!("`{self_descr}` used in trait"));
             } else {
-                err.note_trait_signature(trait_m.name, trait_m.signature(tcx));
+                err.note_trait_signature(trait_m.name(), trait_m.signature(tcx));
             }
 
             return Err(err.emit_unless(delay));
@@ -1421,7 +1423,7 @@ fn compare_number_of_generics<'tcx>(
                     "{} `{}` has {} {kind} parameter{} but its trait \
                      declaration has {} {kind} parameter{}",
                     item_kind,
-                    trait_.name,
+                    trait_.name(),
                     impl_count,
                     pluralize!(impl_count),
                     trait_count,
@@ -1512,7 +1514,7 @@ fn compare_number_of_method_arguments<'tcx>(
             impl_span,
             E0050,
             "method `{}` has {} but the declaration in trait `{}` has {}",
-            trait_m.name,
+            trait_m.name(),
             potentially_plural_count(impl_number_args, "parameter"),
             tcx.def_path_str(trait_m.def_id),
             trait_number_args
@@ -1527,7 +1529,7 @@ fn compare_number_of_method_arguments<'tcx>(
                 ),
             );
         } else {
-            err.note_trait_signature(trait_m.name, trait_m.signature(tcx));
+            err.note_trait_signature(trait_m.name(), trait_m.signature(tcx));
         }
 
         err.span_label(
@@ -1581,7 +1583,7 @@ fn compare_synthetic_generics<'tcx>(
                 impl_span,
                 E0643,
                 "method `{}` has incompatible signature for trait",
-                trait_m.name
+                trait_m.name()
             );
             err.span_label(trait_span, "declaration in trait here");
             if impl_synthetic {
@@ -1741,7 +1743,7 @@ fn compare_generic_param_kinds<'tcx>(
                 E0053,
                 "{} `{}` has an incompatible generic parameter for trait `{}`",
                 impl_item.descr(),
-                trait_item.name,
+                trait_item.name(),
                 &tcx.def_path_str(tcx.parent(trait_item.def_id))
             );
 
@@ -1877,7 +1879,7 @@ fn compare_const_predicate_entailment<'tcx>(
             cause.span,
             E0326,
             "implemented const `{}` has an incompatible type for trait",
-            trait_ct.name
+            trait_ct.name()
         );
 
         let trait_c_span = trait_ct.def_id.as_local().map(|trait_ct_def_id| {
@@ -2237,8 +2239,8 @@ fn param_env_with_gat_bounds<'tcx>(
     // bounds about themselves.
     let impl_tys_to_install = match impl_ty.kind {
         ty::AssocKind::Type {
-            opt_rpitit_info:
-                Some(
+            data:
+                ty::AssocTypeData::Rpitit(
                     ty::ImplTraitInTraitData::Impl { fn_def_id }
                     | ty::ImplTraitInTraitData::Trait { fn_def_id, .. },
                 ),
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index ec934b1f620dd..5fbd771976bbb 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -205,7 +205,7 @@ fn missing_items_err(
 
     let missing_items_msg = missing_items
         .clone()
-        .map(|trait_item| trait_item.name.to_string())
+        .map(|trait_item| trait_item.name().to_string())
         .collect::<Vec<_>>()
         .join("`, `");
 
@@ -236,7 +236,7 @@ fn missing_items_err(
         let code = format!("{padding}{snippet}\n{padding}");
         if let Some(span) = tcx.hir_span_if_local(trait_item.def_id) {
             missing_trait_item_label
-                .push(errors::MissingTraitItemLabel { span, item: trait_item.name });
+                .push(errors::MissingTraitItemLabel { span, item: trait_item.name() });
             missing_trait_item.push(errors::MissingTraitItemSuggestion {
                 span: sugg_sp,
                 code,
@@ -504,9 +504,9 @@ fn suggestion_signature<'tcx>(
                 tcx,
                 tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args),
             );
-            format!("type {}{generics} = /* Type */{where_clauses};", assoc.name)
+            format!("type {}{generics} = /* Type */{where_clauses};", assoc.name())
         }
-        ty::AssocKind::Const => {
+        ty::AssocKind::Const { name } => {
             let ty = tcx.type_of(assoc.def_id).instantiate_identity();
             let val = tcx
                 .infer_ctxt()
@@ -514,7 +514,7 @@ fn suggestion_signature<'tcx>(
                 .err_ctxt()
                 .ty_kind_suggestion(tcx.param_env(assoc.def_id), ty)
                 .unwrap_or_else(|| "value".to_string());
-            format!("const {}: {} = {};", assoc.name, ty, val)
+            format!("const {}: {} = {};", name, ty, val)
         }
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index c6c370c4a8467..33d5a86beb3b0 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -474,7 +474,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
                             gat_generics,
                         )
                     }
-                    ty::AssocKind::Const => None,
+                    ty::AssocKind::Const { .. } => None,
                 };
 
                 if let Some(item_required_bounds) = item_required_bounds {
@@ -1076,7 +1076,7 @@ fn check_associated_item(
         };
 
         match item.kind {
-            ty::AssocKind::Const => {
+            ty::AssocKind::Const { .. } => {
                 let ty = tcx.type_of(item.def_id).instantiate_identity();
                 let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
                 wfcx.register_wf_obligation(span, loc, ty.into());
diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
index cbfad1f6883e5..242639125b19a 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
@@ -51,7 +51,7 @@ impl<'tcx> InherentOverlapChecker<'tcx> {
 
         for &item1 in impl_items1.in_definition_order() {
             let collision = impl_items2
-                .filter_by_name_unhygienic(item1.name)
+                .filter_by_name_unhygienic(item1.name())
                 .any(|&item2| self.compare_hygienically(item1, item2));
 
             if collision {
@@ -113,7 +113,7 @@ impl<'tcx> InherentOverlapChecker<'tcx> {
         let mut res = Ok(());
         for &item1 in impl_items1.in_definition_order() {
             let collision = impl_items2
-                .filter_by_name_unhygienic(item1.name)
+                .filter_by_name_unhygienic(item1.name())
                 .find(|&&item2| self.compare_hygienically(item1, item2));
 
             if let Some(item2) = collision {
@@ -230,11 +230,11 @@ impl<'tcx> InherentOverlapChecker<'tcx> {
                 let mut ids = impl_items
                     .in_definition_order()
                     .filter_map(|item| {
-                        let entry = connected_region_ids.entry(item.name);
+                        let entry = connected_region_ids.entry(item.name());
                         if let IndexEntry::Occupied(e) = &entry {
                             Some(*e.get())
                         } else {
-                            idents_to_add.push(item.name);
+                            idents_to_add.push(item.name());
                             None
                         }
                     })
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index 653adc6b3ba5f..50e20a19edaef 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -32,7 +32,7 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
     for &assoc_id in tcx.associated_item_def_ids(impl_def_id) {
         let assoc = tcx.associated_item(assoc_id);
         match assoc.kind {
-            ty::AssocKind::Const | ty::AssocKind::Fn { .. } => {
+            ty::AssocKind::Const { .. } | ty::AssocKind::Fn { .. } => {
                 locator.check(assoc_id.expect_local())
             }
             // Associated types don't have bodies, so they can't constrain hidden types
diff --git a/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs b/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
index 70d60bfcf2d20..526ee30209c7d 100644
--- a/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
+++ b/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
@@ -492,7 +492,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
                         .gen_args
                         .constraints
                         .iter()
-                        .any(|constraint| constraint.ident.name == item.name)
+                        .any(|constraint| constraint.ident.name == item.name())
                 })
                 .filter(|item| !item.is_impl_trait_in_trait())
                 .map(|item| self.tcx.item_ident(item.def_id).to_string())
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 4f8d5471b6f4d..72f219bfeb802 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -168,7 +168,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let all_candidate_names: Vec<_> = all_candidates()
             .flat_map(|r| tcx.associated_items(r.def_id()).in_definition_order())
             .filter_map(|item| {
-                (!item.is_impl_trait_in_trait() && item.as_tag() == assoc_tag).then_some(item.name)
+                if !item.is_impl_trait_in_trait() && item.as_tag() == assoc_tag {
+                    item.opt_name()
+                } else {
+                    None
+                }
             })
             .collect();
 
@@ -200,7 +204,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .iter()
             .flat_map(|trait_def_id| tcx.associated_items(*trait_def_id).in_definition_order())
             .filter_map(|item| {
-                (!item.is_impl_trait_in_trait() && item.as_tag() == assoc_tag).then_some(item.name)
+                (!item.is_impl_trait_in_trait() && item.as_tag() == assoc_tag)
+                    .then_some(item.name())
             })
             .collect();
 
@@ -337,7 +342,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     ) -> ErrorGuaranteed {
         let tcx = self.tcx();
 
-        let bound_on_assoc_const_label = if let ty::AssocKind::Const = assoc_item.kind
+        let bound_on_assoc_const_label = if let ty::AssocKind::Const { .. } = assoc_item.kind
             && let Some(constraint) = constraint
             && let hir::AssocItemConstraintKind::Bound { .. } = constraint.kind
         {
@@ -761,7 +766,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // `issue-22560.rs`.
         let mut dyn_compatibility_violations = Ok(());
         for (assoc_item, trait_ref) in &missing_assoc_types {
-            names.entry(trait_ref).or_default().push(assoc_item.name);
+            names.entry(trait_ref).or_default().push(assoc_item.name());
             names_len += 1;
 
             let violations =
@@ -852,16 +857,17 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let mut names: UnordMap<_, usize> = Default::default();
         for (item, _) in &missing_assoc_types {
             types_count += 1;
-            *names.entry(item.name).or_insert(0) += 1;
+            *names.entry(item.name()).or_insert(0) += 1;
         }
         let mut dupes = false;
         let mut shadows = false;
         for (item, trait_ref) in &missing_assoc_types {
-            let prefix = if names[&item.name] > 1 {
+            let name = item.name();
+            let prefix = if names[&name] > 1 {
                 let trait_def_id = trait_ref.def_id();
                 dupes = true;
                 format!("{}::", tcx.def_path_str(trait_def_id))
-            } else if bound_names.get(&item.name).is_some_and(|x| *x != item) {
+            } else if bound_names.get(&name).is_some_and(|x| *x != item) {
                 let trait_def_id = trait_ref.def_id();
                 shadows = true;
                 format!("{}::", tcx.def_path_str(trait_def_id))
@@ -871,7 +877,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
             let mut is_shadowed = false;
 
-            if let Some(assoc_item) = bound_names.get(&item.name)
+            if let Some(assoc_item) = bound_names.get(&name)
                 && *assoc_item != item
             {
                 is_shadowed = true;
@@ -880,17 +886,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     if assoc_item.def_id.is_local() { ", consider renaming it" } else { "" };
                 err.span_label(
                     tcx.def_span(assoc_item.def_id),
-                    format!("`{}{}` shadowed here{}", prefix, item.name, rename_message),
+                    format!("`{}{}` shadowed here{}", prefix, name, rename_message),
                 );
             }
 
             let rename_message = if is_shadowed { ", consider renaming it" } else { "" };
 
             if let Some(sp) = tcx.hir_span_if_local(item.def_id) {
-                err.span_label(
-                    sp,
-                    format!("`{}{}` defined here{}", prefix, item.name, rename_message),
-                );
+                err.span_label(sp, format!("`{}{}` defined here{}", prefix, name, rename_message));
             }
         }
         if potential_assoc_types.len() == missing_assoc_types.len() {
@@ -903,7 +906,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         {
             let types: Vec<_> = missing_assoc_types
                 .iter()
-                .map(|(item, _)| format!("{} = Type", item.name))
+                .map(|(item, _)| format!("{} = Type", item.name()))
                 .collect();
             let code = if let Some(snippet) = snippet.strip_suffix('>') {
                 // The user wrote `Trait<'a>` or similar and we don't have a type we can
@@ -938,16 +941,17 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             let mut names: FxIndexMap<_, usize> = FxIndexMap::default();
             for (item, _) in &missing_assoc_types {
                 types_count += 1;
-                *names.entry(item.name).or_insert(0) += 1;
+                *names.entry(item.name()).or_insert(0) += 1;
             }
             let mut label = vec![];
             for (item, trait_ref) in &missing_assoc_types {
-                let postfix = if names[&item.name] > 1 {
+                let name = item.name();
+                let postfix = if names[&name] > 1 {
                     format!(" (from trait `{}`)", trait_ref.print_trait_sugared())
                 } else {
                     String::new()
                 };
-                label.push(format!("`{}`{}", item.name, postfix));
+                label.push(format!("`{}`{}", name, postfix));
             }
             if !label.is_empty() {
                 err.span_label(
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
index 49fd55b03a255..483b61add3380 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
@@ -502,7 +502,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .associated_items(trait_def_id)
             .in_definition_order()
             .filter(|assoc| assoc.namespace() == Namespace::ValueNS)
-            .map(|cand| cand.name)
+            .map(|cand| cand.name())
             .collect();
         if let Some(typo) = find_best_match_for_name(&names, segment.ident.name, None) {
             diag.span_suggestion_verbose(
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check.rs b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
index 127ca846b9fe0..cbdc501291bc8 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
@@ -119,7 +119,7 @@ pub(crate) fn enforce_impl_lifetime_params_are_constrained(
                         vec![]
                     }
                 }
-                ty::AssocKind::Fn { .. } | ty::AssocKind::Const => vec![],
+                ty::AssocKind::Fn { .. } | ty::AssocKind::Const { .. } => vec![],
             }
         })
         .collect();
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 56c205b6f8794..532c5092a4e94 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2601,8 +2601,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         return None;
                     }
                     let input_len = fn_sig.inputs().skip_binder().len();
-                    let order = !item.name.as_str().starts_with("new");
-                    Some((order, item.name, input_len))
+                    let name = item.name();
+                    let order = !name.as_str().starts_with("new");
+                    Some((order, name, input_len))
                 })
                 .collect::<Vec<_>>();
             items.sort_by_key(|(order, _, _)| *order);
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 3a0f3a4a5f0b7..da0e8e362d663 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -683,10 +683,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     .all(|(expected, found)| self.may_coerce(*expected, *found))
                 && fn_sig.inputs()[1..].len() == input_types.len()
             {
+                let assoc_name = assoc.name();
                 err.span_suggestion_verbose(
                     call_name.span,
-                    format!("you might have meant to use `{}`", assoc.name),
-                    assoc.name,
+                    format!("you might have meant to use `{}`", assoc_name),
+                    assoc_name,
                     Applicability::MaybeIncorrect,
                 );
                 return;
@@ -706,7 +707,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     tcx.def_span(assoc.def_id),
                     format!(
                         "there's is a method with similar name `{}`, but the arguments don't match",
-                        assoc.name,
+                        assoc.name(),
                     ),
                 );
                 return;
@@ -718,7 +719,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     format!(
                         "there's is a method with similar name `{}`, but their argument count \
                          doesn't match",
-                        assoc.name,
+                        assoc.name(),
                     ),
                 );
                 return;
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index 912098c4e2d65..91eb1989864ff 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -381,9 +381,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let mut suggestions = methods
                 .iter()
                 .filter_map(|conversion_method| {
+                    let conversion_method_name = conversion_method.name();
                     let receiver_method_ident = expr.method_ident();
                     if let Some(method_ident) = receiver_method_ident
-                        && method_ident.name == conversion_method.name
+                        && method_ident.name == conversion_method_name
                     {
                         return None; // do not suggest code that is already there (#53348)
                     }
@@ -391,20 +392,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let method_call_list = [sym::to_vec, sym::to_string];
                     let mut sugg = if let ExprKind::MethodCall(receiver_method, ..) = expr.kind
                         && receiver_method.ident.name == sym::clone
-                        && method_call_list.contains(&conversion_method.name)
+                        && method_call_list.contains(&conversion_method_name)
                     // If receiver is `.clone()` and found type has one of those methods,
                     // we guess that the user wants to convert from a slice type (`&[]` or `&str`)
                     // to an owned type (`Vec` or `String`). These conversions clone internally,
                     // so we remove the user's `clone` call.
                     {
-                        vec![(receiver_method.ident.span, conversion_method.name.to_string())]
+                        vec![(receiver_method.ident.span, conversion_method_name.to_string())]
                     } else if expr.precedence() < ExprPrecedence::Unambiguous {
                         vec![
                             (expr.span.shrink_to_lo(), "(".to_string()),
-                            (expr.span.shrink_to_hi(), format!(").{}()", conversion_method.name)),
+                            (expr.span.shrink_to_hi(), format!(").{}()", conversion_method_name)),
                         ]
                     } else {
-                        vec![(expr.span.shrink_to_hi(), format!(".{}()", conversion_method.name))]
+                        vec![(expr.span.shrink_to_hi(), format!(".{}()", conversion_method_name))]
                     };
                     let struct_pat_shorthand_field =
                         self.tcx.hir_maybe_get_struct_pattern_shorthand_field(expr);
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index 1d86ff14471a5..0c6240d1f74bd 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -266,7 +266,7 @@ fn infer_type_if_missing<'tcx>(fcx: &FnCtxt<'_, 'tcx>, node: Node<'tcx>) -> Opti
     let expected_type = if let Some(&hir::Ty { kind: hir::TyKind::Infer(()), span, .. }) = node.ty()
     {
         if let Some(item) = tcx.opt_associated_item(def_id.into())
-            && let ty::AssocKind::Const = item.kind
+            && let ty::AssocKind::Const { .. } = item.kind
             && let ty::AssocItemContainer::Impl = item.container
             && let Some(trait_item_def_id) = item.trait_item_def_id
         {
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index c14b7823e3703..ba4396a5ab35b 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -1671,7 +1671,7 @@ impl<'tcx> Pick<'tcx> {
     /// Do not use for type checking.
     pub(crate) fn differs_from(&self, other: &Self) -> bool {
         let Self {
-            item: AssocItem { def_id, name: _, kind: _, container: _, trait_item_def_id: _ },
+            item: AssocItem { def_id, kind: _, container: _, trait_item_def_id: _ },
             kind: _,
             import_ids: _,
             autoderefs: _,
@@ -1714,17 +1714,12 @@ impl<'tcx> Pick<'tcx> {
                         tcx.def_path_str(self.item.def_id),
                     ));
                 }
-                (ty::AssocKind::Const, ty::AssocItemContainer::Trait) => {
+                (ty::AssocKind::Const { name }, ty::AssocItemContainer::Trait) => {
                     let def_id = self.item.container_id(tcx);
                     lint.span_suggestion(
                         span,
                         "use the fully qualified path to the associated const",
-                        format!(
-                            "<{} as {}>::{}",
-                            self.self_ty,
-                            tcx.def_path_str(def_id),
-                            self.item.name
-                        ),
+                        format!("<{} as {}>::{}", self.self_ty, tcx.def_path_str(def_id), name),
                         Applicability::MachineApplicable,
                     );
                 }
@@ -2213,7 +2208,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 let best_name = {
                     let names = applicable_close_candidates
                         .iter()
-                        .map(|cand| cand.name)
+                        .map(|cand| cand.name())
                         .collect::<Vec<Symbol>>();
                     find_best_match_for_name_with_substrings(
                         &names,
@@ -2225,10 +2220,12 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     applicable_close_candidates
                         .iter()
                         .find(|cand| self.matches_by_doc_alias(cand.def_id))
-                        .map(|cand| cand.name)
+                        .map(|cand| cand.name())
                 });
                 Ok(best_name.and_then(|best_name| {
-                    applicable_close_candidates.into_iter().find(|method| method.name == best_name)
+                    applicable_close_candidates
+                        .into_iter()
+                        .find(|method| method.name() == best_name)
                 }))
             }
         })
@@ -2246,7 +2243,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             Mode::MethodCall => item.is_method(),
             Mode::Path => match item.kind {
                 ty::AssocKind::Type { .. } => false,
-                ty::AssocKind::Fn { .. } | ty::AssocKind::Const => true,
+                ty::AssocKind::Fn { .. } | ty::AssocKind::Const { .. } => true,
             },
         }
         // FIXME -- check for types that deref to `Self`,
@@ -2320,7 +2317,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     fn is_relevant_kind_for_mode(&self, kind: ty::AssocKind) -> bool {
         match (self.mode, kind) {
             (Mode::MethodCall, ty::AssocKind::Fn { .. }) => true,
-            (Mode::Path, ty::AssocKind::Const | ty::AssocKind::Fn { .. }) => true,
+            (Mode::Path, ty::AssocKind::Const { .. } | ty::AssocKind::Fn { .. }) => true,
             _ => false,
         }
     }
@@ -2402,7 +2399,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         }
                         match edit_distance_with_substrings(
                             name.as_str(),
-                            x.name.as_str(),
+                            x.name().as_str(),
                             max_dist,
                         ) {
                             Some(d) => d > 0,
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 962871ed2d112..6a9fd7cdd483b 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -1722,7 +1722,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // that had unsatisfied trait bounds
             if unsatisfied_predicates.is_empty()
                 // ...or if we already suggested that name because of `rustc_confusable` annotation.
-                && Some(similar_candidate.name) != confusable_suggested
+                && Some(similar_candidate.name()) != confusable_suggested
             {
                 self.find_likely_intended_associated_item(
                     &mut err,
@@ -1821,10 +1821,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let tcx = self.tcx;
         let def_kind = similar_candidate.as_def_kind();
         let an = self.tcx.def_kind_descr_article(def_kind, similar_candidate.def_id);
+        let similar_candidate_name = similar_candidate.name();
         let msg = format!(
             "there is {an} {} `{}` with a similar name",
             self.tcx.def_kind_descr(def_kind, similar_candidate.def_id),
-            similar_candidate.name,
+            similar_candidate_name,
         );
         // Methods are defined within the context of a struct and their first parameter
         // is always `self`, which represents the instance of the struct the method is
@@ -1843,7 +1844,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     err.span_suggestion_verbose(
                         span,
                         msg,
-                        similar_candidate.name,
+                        similar_candidate_name,
                         Applicability::MaybeIncorrect,
                     );
                 } else {
@@ -1865,7 +1866,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 err.span_suggestion_verbose(
                     span,
                     msg,
-                    similar_candidate.name,
+                    similar_candidate_name,
                     Applicability::MaybeIncorrect,
                 );
             } else {
@@ -1878,7 +1879,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             err.span_suggestion_verbose(
                 span,
                 msg,
-                similar_candidate.name,
+                similar_candidate_name,
                 Applicability::MaybeIncorrect,
             );
         } else {
@@ -1918,6 +1919,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             infer::FnCall,
                             fn_sig,
                         );
+                        let name = inherent_method.name();
                         if let Some(ref args) = call_args
                             && fn_sig.inputs()[1..]
                                 .iter()
@@ -1927,20 +1929,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         {
                             err.span_suggestion_verbose(
                                 item_name.span,
-                                format!("you might have meant to use `{}`", inherent_method.name),
-                                inherent_method.name,
+                                format!("you might have meant to use `{}`", name),
+                                name,
                                 Applicability::MaybeIncorrect,
                             );
-                            return Some(inherent_method.name);
+                            return Some(name);
                         } else if let None = call_args {
                             err.span_note(
                                 self.tcx.def_span(inherent_method.def_id),
-                                format!(
-                                    "you might have meant to use method `{}`",
-                                    inherent_method.name,
-                                ),
+                                format!("you might have meant to use method `{}`", name),
                             );
-                            return Some(inherent_method.name);
+                            return Some(name);
                         }
                     }
                 }
@@ -2116,7 +2115,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Only assoc fn with no receivers and only if
             // they are resolvable
             .filter(|item| {
-                matches!(item.kind, ty::AssocKind::Fn { has_self: false })
+                matches!(item.kind, ty::AssocKind::Fn { has_self: false, .. })
                     && self
                         .probe_for_name(
                             Mode::Path,
diff --git a/compiler/rustc_hir_typeck/src/op.rs b/compiler/rustc_hir_typeck/src/op.rs
index 93f77b8409f00..0e42a84ca32ae 100644
--- a/compiler/rustc_hir_typeck/src/op.rs
+++ b/compiler/rustc_hir_typeck/src/op.rs
@@ -372,7 +372,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 .associated_item_def_ids(def_id)
                                 .iter()
                                 .find(|item_def_id| {
-                                    self.tcx.associated_item(*item_def_id).name == sym::Output
+                                    self.tcx.associated_item(*item_def_id).name() == sym::Output
                                 })
                                 .cloned()
                         });
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 3cbe09280f690..3c2245347f97c 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1332,30 +1332,26 @@ impl<'a> CrateMetadataRef<'a> {
     }
 
     fn get_associated_item(self, id: DefIndex, sess: &'a Session) -> ty::AssocItem {
-        let name = if self.root.tables.opt_rpitit_info.get(self, id).is_some() {
-            kw::Empty
-        } else {
-            self.item_name(id)
-        };
         let kind = match self.def_kind(id) {
-            DefKind::AssocConst => ty::AssocKind::Const,
-            DefKind::AssocFn => {
-                ty::AssocKind::Fn { has_self: self.get_fn_has_self_parameter(id, sess) }
-            }
-            DefKind::AssocTy => ty::AssocKind::Type {
-                opt_rpitit_info: self
-                    .root
-                    .tables
-                    .opt_rpitit_info
-                    .get(self, id)
-                    .map(|d| d.decode(self)),
+            DefKind::AssocConst => ty::AssocKind::Const { name: self.item_name(id) },
+            DefKind::AssocFn => ty::AssocKind::Fn {
+                name: self.item_name(id),
+                has_self: self.get_fn_has_self_parameter(id, sess),
             },
+            DefKind::AssocTy => {
+                let data = if let Some(rpitit_info) = self.root.tables.opt_rpitit_info.get(self, id)
+                {
+                    ty::AssocTypeData::Rpitit(rpitit_info.decode(self))
+                } else {
+                    ty::AssocTypeData::Normal(self.item_name(id))
+                };
+                ty::AssocKind::Type { data }
+            }
             _ => bug!("cannot get associated-item of `{:?}`", self.def_key(id)),
         };
         let container = self.root.tables.assoc_container.get(self, id).unwrap();
 
         ty::AssocItem {
-            name,
             kind,
             def_id: self.local_def_id(id),
             trait_item_def_id: self.get_trait_item_def_id(id),
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index b900100c3c011..177318bfe15e9 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1706,7 +1706,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 }
             }
         }
-        if let ty::AssocKind::Type { opt_rpitit_info: Some(rpitit_info) } = item.kind {
+        if let ty::AssocKind::Type { data: ty::AssocTypeData::Rpitit(rpitit_info) } = item.kind {
             record!(self.tables.opt_rpitit_info[def_id] <- rpitit_info);
             if matches!(rpitit_info, ty::ImplTraitInTraitData::Trait { .. }) {
                 record_array!(
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index 6138157d83626..0c44fd2758d52 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -18,7 +18,6 @@ pub enum AssocItemContainer {
 #[derive(Copy, Clone, Debug, PartialEq, HashStable, Eq, Hash, Encodable, Decodable)]
 pub struct AssocItem {
     pub def_id: DefId,
-    pub name: Symbol,
     pub kind: AssocKind,
     pub container: AssocItemContainer,
 
@@ -28,8 +27,24 @@ pub struct AssocItem {
 }
 
 impl AssocItem {
+    // Gets the identifier, if it has one.
+    pub fn opt_name(&self) -> Option<Symbol> {
+        match self.kind {
+            ty::AssocKind::Type { data: AssocTypeData::Normal(name) } => Some(name),
+            ty::AssocKind::Type { data: AssocTypeData::Rpitit(_) } => None,
+            ty::AssocKind::Const { name } => Some(name),
+            ty::AssocKind::Fn { name, .. } => Some(name),
+        }
+    }
+
+    // Gets the identifier name. Aborts if it lacks one, i.e. is an RPITIT
+    // associated type.
+    pub fn name(&self) -> Symbol {
+        self.opt_name().expect("name of non-Rpitit assoc item")
+    }
+
     pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
-        Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap())
+        Ident::new(self.name(), tcx.def_ident_span(self.def_id).unwrap())
     }
 
     /// Gets the defaultness of the associated item.
@@ -76,22 +91,18 @@ impl AssocItem {
                 // regions just fine, showing `fn(&MyType)`.
                 tcx.fn_sig(self.def_id).instantiate_identity().skip_binder().to_string()
             }
-            ty::AssocKind::Type { .. } => format!("type {};", self.name),
-            ty::AssocKind::Const => {
-                format!(
-                    "const {}: {:?};",
-                    self.name,
-                    tcx.type_of(self.def_id).instantiate_identity()
-                )
+            ty::AssocKind::Type { .. } => format!("type {};", self.name()),
+            ty::AssocKind::Const { name } => {
+                format!("const {}: {:?};", name, tcx.type_of(self.def_id).instantiate_identity())
             }
         }
     }
 
     pub fn descr(&self) -> &'static str {
         match self.kind {
-            ty::AssocKind::Const => "associated const",
-            ty::AssocKind::Fn { has_self: true } => "method",
-            ty::AssocKind::Fn { has_self: false } => "associated function",
+            ty::AssocKind::Const { .. } => "associated const",
+            ty::AssocKind::Fn { has_self: true, .. } => "method",
+            ty::AssocKind::Fn { has_self: false, .. } => "associated function",
             ty::AssocKind::Type { .. } => "associated type",
         }
     }
@@ -99,13 +110,13 @@ impl AssocItem {
     pub fn namespace(&self) -> Namespace {
         match self.kind {
             ty::AssocKind::Type { .. } => Namespace::TypeNS,
-            ty::AssocKind::Const | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
+            ty::AssocKind::Const { .. } | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
         }
     }
 
     pub fn as_def_kind(&self) -> DefKind {
         match self.kind {
-            AssocKind::Const => DefKind::AssocConst,
+            AssocKind::Const { .. } => DefKind::AssocConst,
             AssocKind::Fn { .. } => DefKind::AssocFn,
             AssocKind::Type { .. } => DefKind::AssocTy,
         }
@@ -119,19 +130,19 @@ impl AssocItem {
     }
 
     pub fn is_method(&self) -> bool {
-        matches!(self.kind, ty::AssocKind::Fn { has_self: true })
+        matches!(self.kind, ty::AssocKind::Fn { has_self: true, .. })
     }
 
     pub fn as_tag(&self) -> AssocTag {
         match self.kind {
-            AssocKind::Const => AssocTag::Const,
+            AssocKind::Const { .. } => AssocTag::Const,
             AssocKind::Fn { .. } => AssocTag::Fn,
             AssocKind::Type { .. } => AssocTag::Type,
         }
     }
 
     pub fn is_impl_trait_in_trait(&self) -> bool {
-        matches!(self.kind, AssocKind::Type { opt_rpitit_info: Some(_) })
+        matches!(self.kind, AssocKind::Type { data: AssocTypeData::Rpitit(_) })
     }
 
     /// Returns true if:
@@ -139,7 +150,7 @@ impl AssocItem {
     /// - If it is in a trait impl, the item from the original trait has this attribute, or
     /// - It is an inherent assoc const.
     pub fn is_type_const_capable(&self, tcx: TyCtxt<'_>) -> bool {
-        if self.kind != ty::AssocKind::Const {
+        if !matches!(self.kind, ty::AssocKind::Const { .. }) {
             return false;
         }
 
@@ -153,26 +164,45 @@ impl AssocItem {
     }
 }
 
+#[derive(Copy, Clone, PartialEq, Debug, HashStable, Eq, Hash, Encodable, Decodable)]
+pub enum AssocTypeData {
+    Normal(Symbol),
+    /// The associated type comes from an RPITIT. It has no name, and the
+    /// `ImplTraitInTraitData` provides additional information about its
+    /// source.
+    Rpitit(ty::ImplTraitInTraitData),
+}
+
 #[derive(Copy, Clone, PartialEq, Debug, HashStable, Eq, Hash, Encodable, Decodable)]
 pub enum AssocKind {
-    Const,
-    Fn {
-        has_self: bool,
-    },
-    Type {
-        /// `Some` if the associated type comes from an RPITIT. The
-        /// `ImplTraitInTraitData` provides additional information about its
-        /// source.
-        opt_rpitit_info: Option<ty::ImplTraitInTraitData>,
-    },
+    Const { name: Symbol },
+    Fn { name: Symbol, has_self: bool },
+    Type { data: AssocTypeData },
+}
+
+impl AssocKind {
+    pub fn namespace(&self) -> Namespace {
+        match *self {
+            ty::AssocKind::Type { .. } => Namespace::TypeNS,
+            ty::AssocKind::Const { .. } | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
+        }
+    }
+
+    pub fn as_def_kind(&self) -> DefKind {
+        match self {
+            AssocKind::Const { .. } => DefKind::AssocConst,
+            AssocKind::Fn { .. } => DefKind::AssocFn,
+            AssocKind::Type { .. } => DefKind::AssocTy,
+        }
+    }
 }
 
 impl std::fmt::Display for AssocKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            AssocKind::Fn { has_self: true } => write!(f, "method"),
-            AssocKind::Fn { has_self: false } => write!(f, "associated function"),
-            AssocKind::Const => write!(f, "associated const"),
+            AssocKind::Fn { has_self: true, .. } => write!(f, "method"),
+            AssocKind::Fn { has_self: false, .. } => write!(f, "associated function"),
+            AssocKind::Const { .. } => write!(f, "associated const"),
             AssocKind::Type { .. } => write!(f, "associated type"),
         }
     }
@@ -193,17 +223,17 @@ pub enum AssocTag {
 /// done only on items with the same name.
 #[derive(Debug, Clone, PartialEq, HashStable)]
 pub struct AssocItems {
-    items: SortedIndexMultiMap<u32, Symbol, ty::AssocItem>,
+    items: SortedIndexMultiMap<u32, Option<Symbol>, ty::AssocItem>,
 }
 
 impl AssocItems {
     /// Constructs an `AssociatedItems` map from a series of `ty::AssocItem`s in definition order.
     pub fn new(items_in_def_order: impl IntoIterator<Item = ty::AssocItem>) -> Self {
-        let items = items_in_def_order.into_iter().map(|item| (item.name, item)).collect();
+        let items = items_in_def_order.into_iter().map(|item| (item.opt_name(), item)).collect();
         AssocItems { items }
     }
 
-    /// Returns a slice of associated items in the order they were defined.
+    /// Returns an iterator over associated items in the order they were defined.
     ///
     /// New code should avoid relying on definition order. If you need a particular associated item
     /// for a known trait, make that trait a lang item instead of indexing this array.
@@ -220,7 +250,8 @@ impl AssocItems {
         &self,
         name: Symbol,
     ) -> impl '_ + Iterator<Item = &ty::AssocItem> {
-        self.items.get_by_key(name)
+        assert!(!name.is_empty());
+        self.items.get_by_key(Some(name))
     }
 
     /// Returns the associated item with the given identifier and `AssocKind`, if one exists.
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 395d2ec48142c..1945538b1c2f0 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -1611,9 +1611,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// about where that RPITIT came from.
     pub fn opt_rpitit_info(self, def_id: DefId) -> Option<ImplTraitInTraitData> {
         if let DefKind::AssocTy = self.def_kind(def_id)
-            && let AssocKind::Type { opt_rpitit_info } = self.associated_item(def_id).kind
+            && let AssocKind::Type { data: AssocTypeData::Rpitit(rpitit_info) } =
+                self.associated_item(def_id).kind
         {
-            opt_rpitit_info
+            Some(rpitit_info)
         } else {
             None
         }
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 2f93197bcef13..d739218af5ee7 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1214,7 +1214,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                             && assoc
                                 .trait_container(tcx)
                                 .is_some_and(|def_id| tcx.is_lang_item(def_id, LangItem::Coroutine))
-                            && assoc.name == rustc_span::sym::Return
+                            && assoc.opt_name() == Some(rustc_span::sym::Return)
                         {
                             if let ty::Coroutine(_, args) = args.type_at(0).kind() {
                                 let return_ty = args.as_coroutine().return_ty();
@@ -1237,7 +1237,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                             p!(", ");
                         }
 
-                        p!(write("{} = ", tcx.associated_item(assoc_item_def_id).name));
+                        p!(write("{} = ", tcx.associated_item(assoc_item_def_id).name()));
 
                         match term.unpack() {
                             TermKind::Ty(ty) => p!(print(ty)),
@@ -3291,7 +3291,7 @@ define_print! {
     }
 
     ty::ExistentialProjection<'tcx> {
-        let name = cx.tcx().associated_item(self.def_id).name;
+        let name = cx.tcx().associated_item(self.def_id).name();
         // The args don't contain the self ty (as it has been erased) but the corresp.
         // generics do as the trait always has a self ty param. We need to offset.
         let args = &self.args[cx.tcx().generics_of(self.def_id).parent_count - 1..];
diff --git a/compiler/rustc_mir_transform/src/check_undefined_transmutes.rs b/compiler/rustc_mir_transform/src/check_undefined_transmutes.rs
index ed3b1ae4f42f1..daddb5dedbcf9 100644
--- a/compiler/rustc_mir_transform/src/check_undefined_transmutes.rs
+++ b/compiler/rustc_mir_transform/src/check_undefined_transmutes.rs
@@ -42,7 +42,7 @@ impl<'a, 'tcx> UndefinedTransmutesChecker<'a, 'tcx> {
         if self.tcx.is_const_fn(def_id)
             || matches!(
                 self.tcx.opt_associated_item(def_id),
-                Some(AssocItem { kind: AssocKind::Const, .. })
+                Some(AssocItem { kind: AssocKind::Const { .. }, .. })
             )
         {
             let fn_sig = function.ty(self.body, self.tcx).fn_sig(self.tcx).skip_binder();
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index ae81021e0bea1..d4fe446cc9f76 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -2007,8 +2007,9 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 if def.did() != def_id {
                     return None;
                 }
-                let order = !item.name.as_str().starts_with("new");
-                Some((order, item.name, input_len))
+                let name = item.name();
+                let order = !name.as_str().starts_with("new");
+                Some((order, name, input_len))
             })
             .collect::<Vec<_>>();
         items.sort_by_key(|(order, _, _)| *order);
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
index 55f698b8f211f..a757329bcf2ae 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
@@ -895,12 +895,19 @@ impl<'tcx> Stable<'tcx> for ty::AssocKind {
     type T = stable_mir::ty::AssocKind;
 
     fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
-        use stable_mir::ty::AssocKind;
+        use stable_mir::ty::{AssocKind, AssocTypeData};
         match *self {
-            ty::AssocKind::Const => AssocKind::Const,
-            ty::AssocKind::Fn { has_self } => AssocKind::Fn { has_self },
-            ty::AssocKind::Type { opt_rpitit_info } => AssocKind::Type {
-                opt_rpitit_info: opt_rpitit_info.map(|rpitit| rpitit.stable(tables)),
+            ty::AssocKind::Const { name } => AssocKind::Const { name: name.to_string() },
+            ty::AssocKind::Fn { name, has_self } => {
+                AssocKind::Fn { name: name.to_string(), has_self }
+            }
+            ty::AssocKind::Type { data } => AssocKind::Type {
+                data: match data {
+                    ty::AssocTypeData::Normal(name) => AssocTypeData::Normal(name.to_string()),
+                    ty::AssocTypeData::Rpitit(rpitit) => {
+                        AssocTypeData::Rpitit(rpitit.stable(tables))
+                    }
+                },
             },
         }
     }
@@ -924,7 +931,6 @@ impl<'tcx> Stable<'tcx> for ty::AssocItem {
     fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
         stable_mir::ty::AssocItem {
             def_id: tables.assoc_def(self.def_id),
-            name: self.name.to_string(),
             kind: self.kind.stable(tables),
             container: self.container.stable(tables),
             trait_item_def_id: self.trait_item_def_id.map(|did| tables.assoc_def(did)),
diff --git a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
index 9fa97763907f1..8a6be0cd37a0b 100644
--- a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
+++ b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
@@ -22,9 +22,9 @@ impl Display for Ty {
 impl Display for AssocKind {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self {
-            AssocKind::Fn { has_self: true } => write!(f, "method"),
-            AssocKind::Fn { has_self: false } => write!(f, "associated function"),
-            AssocKind::Const => write!(f, "associated const"),
+            AssocKind::Fn { has_self: true, .. } => write!(f, "method"),
+            AssocKind::Fn { has_self: false, .. } => write!(f, "associated function"),
+            AssocKind::Const { .. } => write!(f, "associated const"),
             AssocKind::Type { .. } => write!(f, "associated type"),
         }
     }
diff --git a/compiler/rustc_smir/src/stable_mir/ty.rs b/compiler/rustc_smir/src/stable_mir/ty.rs
index 6eac0885d7636..4b153007bd863 100644
--- a/compiler/rustc_smir/src/stable_mir/ty.rs
+++ b/compiler/rustc_smir/src/stable_mir/ty.rs
@@ -1578,7 +1578,6 @@ crate_def! {
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 pub struct AssocItem {
     pub def_id: AssocDef,
-    pub name: Symbol,
     pub kind: AssocKind,
     pub container: AssocItemContainer,
 
@@ -1587,18 +1586,20 @@ pub struct AssocItem {
     pub trait_item_def_id: Option<AssocDef>,
 }
 
+#[derive(Clone, PartialEq, Debug, Eq, Serialize)]
+pub enum AssocTypeData {
+    Normal(Symbol),
+    /// The associated type comes from an RPITIT. It has no name, and the
+    /// `ImplTraitInTraitData` provides additional information about its
+    /// source.
+    Rpitit(ImplTraitInTraitData),
+}
+
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 pub enum AssocKind {
-    Const,
-    Fn {
-        has_self: bool,
-    },
-    Type {
-        /// `Some` if the associated type comes from an RPITIT. The
-        /// `ImplTraitInTraitData` provides additional information about its
-        /// source.
-        opt_rpitit_info: Option<ImplTraitInTraitData>,
-    },
+    Const { name: Symbol },
+    Fn { name: Symbol, has_self: bool },
+    Type { data: AssocTypeData },
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
@@ -1615,6 +1616,6 @@ pub enum ImplTraitInTraitData {
 
 impl AssocItem {
     pub fn is_impl_trait_in_trait(&self) -> bool {
-        matches!(self.kind, AssocKind::Type { opt_rpitit_info: Some(_) })
+        matches!(self.kind, AssocKind::Type { data: AssocTypeData::Rpitit(_) })
     }
 }
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index d28f10ba9e38b..a4e1266e76439 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -615,7 +615,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                         cx.print_def_path(trait_ref.def_id, trait_ref.args)?;
                     }
                     ty::ExistentialPredicate::Projection(projection) => {
-                        let name = cx.tcx.associated_item(projection.def_id).name;
+                        let name = cx.tcx.associated_item(projection.def_id).name();
                         cx.push("p");
                         cx.push_ident(name.as_str());
                         match projection.term.unpack() {
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
index 1c71fe028d4d0..fdd547448f004 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -2340,7 +2340,7 @@ impl<'tcx> ObligationCause<'tcx> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type { .. }, .. } => {
                 ObligationCauseFailureCode::TypeCompat { span, subdiags }
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const { .. }, .. } => {
                 ObligationCauseFailureCode::ConstCompat { span, subdiags }
             }
             ObligationCauseCode::BlockTailExpression(.., hir::MatchSource::TryDesugar(_)) => {
@@ -2404,7 +2404,7 @@ impl<'tcx> ObligationCause<'tcx> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type { .. }, .. } => {
                 "associated type is compatible with trait"
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const { .. }, .. } => {
                 "const is compatible with trait"
             }
             ObligationCauseCode::MainFunctionType => "`main` function has the correct type",
@@ -2428,7 +2428,7 @@ impl IntoDiagArg for ObligationCauseAsDiagArg<'_> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type { .. }, .. } => {
                 "type_compat"
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const { .. }, .. } => {
                 "const_compat"
             }
             ObligationCauseCode::MainFunctionType => "fn_main_correct_type",
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
index 02f21b5465c64..be508c8cee13e 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
@@ -783,7 +783,7 @@ fn foo(&self) -> Self::T { String::new() }
             .in_definition_order()
             .filter(|item| {
                 item.is_fn()
-                    && Some(item.name) != current_method_ident
+                    && Some(item.name()) != current_method_ident
                     && !tcx.is_doc_hidden(item.def_id)
             })
             .filter_map(|item| {
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
index 49c6acedcfa47..df3cce880dd48 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
@@ -1017,7 +1017,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             infer::BoundRegion(_, br, infer::AssocTypeProjection(def_id)) => format!(
                 " for lifetime parameter {}in trait containing associated type `{}`",
                 br_string(br),
-                self.tcx.associated_item(def_id).name
+                self.tcx.associated_item(def_id).name()
             ),
             infer::RegionParameterDefinition(_, name) => {
                 format!(" for lifetime parameter `{name}`")
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
index c4b0ca9cf8fcc..54b50851b74de 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
@@ -348,7 +348,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         && let None = self.tainted_by_errors()
                     {
                         let (verb, noun) = match self.tcx.associated_item(item_id).kind {
-                            ty::AssocKind::Const => ("refer to the", "constant"),
+                            ty::AssocKind::Const { .. } => ("refer to the", "constant"),
                             ty::AssocKind::Fn { .. } => ("call", "function"),
                             // This is already covered by E0223, but this following single match
                             // arm doesn't hurt here.
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index 08b95b450583b..7d95a7b3fed24 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2112,7 +2112,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         trait_ref: DefId,
     ) {
         if let Some(assoc_item) = self.tcx.opt_associated_item(item_def_id) {
-            if let ty::AssocKind::Const | ty::AssocKind::Type { .. } = assoc_item.kind {
+            if let ty::AssocKind::Const { .. } | ty::AssocKind::Type { .. } = assoc_item.kind {
                 err.note(format!(
                     "{}s cannot be accessed directly on a `trait`, they can only be \
                         accessed through a specific `impl`",
@@ -2121,7 +2121,11 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 err.span_suggestion(
                     span,
                     "use the fully qualified path to an implementation",
-                    format!("<Type as {}>::{}", self.tcx.def_path_str(trait_ref), assoc_item.name),
+                    format!(
+                        "<Type as {}>::{}",
+                        self.tcx.def_path_str(trait_ref),
+                        assoc_item.name()
+                    ),
                     Applicability::HasPlaceholders,
                 );
             }
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index 1ef16f34702ea..519394685a8e7 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -298,31 +298,33 @@ pub fn dyn_compatibility_violations_for_assoc_item(
     match item.kind {
         // Associated consts are never dyn-compatible, as they can't have `where` bounds yet at all,
         // and associated const bounds in trait objects aren't a thing yet either.
-        ty::AssocKind::Const => {
-            vec![DynCompatibilityViolation::AssocConst(item.name, item.ident(tcx).span)]
+        ty::AssocKind::Const { name } => {
+            vec![DynCompatibilityViolation::AssocConst(name, item.ident(tcx).span)]
         }
-        ty::AssocKind::Fn { .. } => virtual_call_violations_for_method(tcx, trait_def_id, item)
-            .into_iter()
-            .map(|v| {
-                let node = tcx.hir_get_if_local(item.def_id);
-                // Get an accurate span depending on the violation.
-                let span = match (&v, node) {
-                    (MethodViolationCode::ReferencesSelfInput(Some(span)), _) => *span,
-                    (MethodViolationCode::UndispatchableReceiver(Some(span)), _) => *span,
-                    (MethodViolationCode::ReferencesImplTraitInTrait(span), _) => *span,
-                    (MethodViolationCode::ReferencesSelfOutput, Some(node)) => {
-                        node.fn_decl().map_or(item.ident(tcx).span, |decl| decl.output.span())
-                    }
-                    _ => item.ident(tcx).span,
-                };
+        ty::AssocKind::Fn { name, .. } => {
+            virtual_call_violations_for_method(tcx, trait_def_id, item)
+                .into_iter()
+                .map(|v| {
+                    let node = tcx.hir_get_if_local(item.def_id);
+                    // Get an accurate span depending on the violation.
+                    let span = match (&v, node) {
+                        (MethodViolationCode::ReferencesSelfInput(Some(span)), _) => *span,
+                        (MethodViolationCode::UndispatchableReceiver(Some(span)), _) => *span,
+                        (MethodViolationCode::ReferencesImplTraitInTrait(span), _) => *span,
+                        (MethodViolationCode::ReferencesSelfOutput, Some(node)) => {
+                            node.fn_decl().map_or(item.ident(tcx).span, |decl| decl.output.span())
+                        }
+                        _ => item.ident(tcx).span,
+                    };
 
-                DynCompatibilityViolation::Method(item.name, v, span)
-            })
-            .collect(),
+                    DynCompatibilityViolation::Method(name, v, span)
+                })
+                .collect()
+        }
         // Associated types can only be dyn-compatible if they have `Self: Sized` bounds.
         ty::AssocKind::Type { .. } => {
             if !tcx.generics_of(item.def_id).is_own_empty() && !item.is_impl_trait_in_trait() {
-                vec![DynCompatibilityViolation::GAT(item.name, item.ident(tcx).span)]
+                vec![DynCompatibilityViolation::GAT(item.name(), item.ident(tcx).span)]
             } else {
                 // We will permit associated types if they are explicitly mentioned in the trait object.
                 // We can't check this here, as here we only check if it is guaranteed to not be possible.
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 83591219b14dc..0dce504903ca4 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1393,7 +1393,7 @@ fn confirm_future_candidate<'cx, 'tcx>(
         coroutine_sig,
     );
 
-    debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Output);
+    debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name(), sym::Output);
 
     let predicate = ty::ProjectionPredicate {
         projection_term: ty::AliasTerm::new_from_args(
@@ -1439,7 +1439,7 @@ fn confirm_iterator_candidate<'cx, 'tcx>(
         gen_sig,
     );
 
-    debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Item);
+    debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name(), sym::Item);
 
     let predicate = ty::ProjectionPredicate {
         projection_term: ty::AliasTerm::new_from_args(
@@ -1485,7 +1485,7 @@ fn confirm_async_iterator_candidate<'cx, 'tcx>(
         gen_sig,
     );
 
-    debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Item);
+    debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name(), sym::Item);
 
     let ty::Adt(_poll_adt, args) = *yield_ty.kind() else {
         bug!();
@@ -2005,7 +2005,8 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     if !assoc_ty.item.defaultness(tcx).has_value() {
         debug!(
             "confirm_impl_candidate: no associated type {:?} for {:?}",
-            assoc_ty.item.name, obligation.predicate
+            assoc_ty.item.name(),
+            obligation.predicate
         );
         if tcx.impl_self_is_guaranteed_unsized(impl_def_id) {
             // We treat this projection as rigid here, which is represented via
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index 2275fbb97923b..6cb9fdc6f931f 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -6,7 +6,6 @@ use rustc_hir::{self as hir, AmbigArg};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, ImplTraitInTraitData, TyCtxt};
 use rustc_middle::{bug, span_bug};
-use rustc_span::kw;
 
 pub(crate) fn provide(providers: &mut Providers) {
     *providers = Providers {
@@ -129,14 +128,14 @@ fn associated_item(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::AssocItem {
 
 fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty::AssocItem {
     let owner_id = trait_item_ref.id.owner_id;
+    let name = trait_item_ref.ident.name;
     let kind = match trait_item_ref.kind {
-        hir::AssocItemKind::Const => ty::AssocKind::Const,
-        hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { has_self },
-        hir::AssocItemKind::Type => ty::AssocKind::Type { opt_rpitit_info: None },
+        hir::AssocItemKind::Const => ty::AssocKind::Const { name },
+        hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { name, has_self },
+        hir::AssocItemKind::Type => ty::AssocKind::Type { data: ty::AssocTypeData::Normal(name) },
     };
 
     ty::AssocItem {
-        name: trait_item_ref.ident.name,
         kind,
         def_id: owner_id.to_def_id(),
         trait_item_def_id: Some(owner_id.to_def_id()),
@@ -146,14 +145,14 @@ fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty
 
 fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::AssocItem {
     let def_id = impl_item_ref.id.owner_id;
+    let name = impl_item_ref.ident.name;
     let kind = match impl_item_ref.kind {
-        hir::AssocItemKind::Const => ty::AssocKind::Const,
-        hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { has_self },
-        hir::AssocItemKind::Type => ty::AssocKind::Type { opt_rpitit_info: None },
+        hir::AssocItemKind::Const => ty::AssocKind::Const { name },
+        hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { name, has_self },
+        hir::AssocItemKind::Type => ty::AssocKind::Type { data: ty::AssocTypeData::Normal(name) },
     };
 
     ty::AssocItem {
-        name: impl_item_ref.ident.name,
         kind,
         def_id: def_id.to_def_id(),
         trait_item_def_id: impl_item_ref.trait_item_def_id,
@@ -260,9 +259,8 @@ fn associated_type_for_impl_trait_in_trait(
     trait_assoc_ty.def_ident_span(Some(span));
 
     trait_assoc_ty.associated_item(ty::AssocItem {
-        name: kw::Empty,
         kind: ty::AssocKind::Type {
-            opt_rpitit_info: Some(ImplTraitInTraitData::Trait {
+            data: ty::AssocTypeData::Rpitit(ImplTraitInTraitData::Trait {
                 fn_def_id: fn_def_id.to_def_id(),
                 opaque_def_id: opaque_ty_def_id.to_def_id(),
             }),
@@ -313,9 +311,8 @@ fn associated_type_for_impl_trait_in_impl(
     impl_assoc_ty.def_ident_span(Some(span));
 
     impl_assoc_ty.associated_item(ty::AssocItem {
-        name: kw::Empty,
         kind: ty::AssocKind::Type {
-            opt_rpitit_info: Some(ImplTraitInTraitData::Impl {
+            data: ty::AssocTypeData::Rpitit(ImplTraitInTraitData::Impl {
                 fn_def_id: impl_fn_def_id.to_def_id(),
             }),
         },
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 74dbc7d06001d..2a95acc622ea8 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -521,7 +521,7 @@ fn projection_to_path_segment<'tcx>(
     let item = cx.tcx.associated_item(def_id);
     let generics = cx.tcx.generics_of(def_id);
     PathSegment {
-        name: item.name,
+        name: item.name(),
         args: GenericArgs::AngleBracketed {
             args: clean_middle_generic_args(
                 cx,
@@ -1340,7 +1340,7 @@ pub(crate) fn clean_impl_item<'tcx>(
 pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocContext<'_>) -> Item {
     let tcx = cx.tcx;
     let kind = match assoc_item.kind {
-        ty::AssocKind::Const => {
+        ty::AssocKind::Const { .. } => {
             let ty = clean_middle_ty(
                 ty::Binder::dummy(tcx.type_of(assoc_item.def_id).instantiate_identity()),
                 cx,
@@ -1374,7 +1374,7 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
                 }
             }
         }
-        ty::AssocKind::Fn { has_self } => {
+        ty::AssocKind::Fn { has_self, .. } => {
             let mut item = inline::build_function(cx, assoc_item.def_id);
 
             if has_self {
@@ -1413,7 +1413,7 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
             }
         }
         ty::AssocKind::Type { .. } => {
-            let my_name = assoc_item.name;
+            let my_name = assoc_item.name();
 
             fn param_eq_arg(param: &GenericParamDef, arg: &GenericArg) -> bool {
                 match (&param.kind, arg) {
@@ -1554,7 +1554,7 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
         }
     };
 
-    Item::from_def_id_and_parts(assoc_item.def_id, Some(assoc_item.name), kind, cx)
+    Item::from_def_id_and_parts(assoc_item.def_id, Some(assoc_item.name()), kind, cx)
 }
 
 fn first_non_private_clean_path<'tcx>(
@@ -2223,7 +2223,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
 
             Type::QPath(Box::new(QPathData {
                 assoc: PathSegment {
-                    name: cx.tcx.associated_item(def_id).name,
+                    name: cx.tcx.associated_item(def_id).name(),
                     args: GenericArgs::AngleBracketed {
                         args: clean_middle_generic_args(
                             cx,
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 06e75fe1764e0..7786b216112bf 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -2504,7 +2504,7 @@ impl Impl {
         self.trait_
             .as_ref()
             .map(|t| t.def_id())
-            .map(|did| tcx.provided_trait_methods(did).map(|meth| meth.name).collect())
+            .map(|did| tcx.provided_trait_methods(did).map(|meth| meth.name()).collect())
             .unwrap_or_default()
     }
 
diff --git a/src/tools/clippy/clippy_lints/src/assigning_clones.rs b/src/tools/clippy/clippy_lints/src/assigning_clones.rs
index ab34af7c31745..e5439a6d401b9 100644
--- a/src/tools/clippy/clippy_lints/src/assigning_clones.rs
+++ b/src/tools/clippy/clippy_lints/src/assigning_clones.rs
@@ -111,8 +111,8 @@ impl<'tcx> LateLintPass<'tcx> for AssigningClones {
             // Only suggest if `clone_from`/`clone_into` is explicitly implemented
             && resolved_assoc_items.in_definition_order().any(|assoc|
                 match which_trait {
-                    CloneTrait::Clone => assoc.name == sym::clone_from,
-                    CloneTrait::ToOwned => assoc.name.as_str() == "clone_into",
+                    CloneTrait::Clone => assoc.name() == sym::clone_from,
+                    CloneTrait::ToOwned => assoc.name().as_str() == "clone_into",
                 }
             )
             && !clone_source_borrows_from_dest(cx, lhs, rhs.span)
diff --git a/src/tools/clippy/clippy_lints/src/methods/double_ended_iterator_last.rs b/src/tools/clippy/clippy_lints/src/methods/double_ended_iterator_last.rs
index e82211bbf3ef7..b5adc69e9a790 100644
--- a/src/tools/clippy/clippy_lints/src/methods/double_ended_iterator_last.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/double_ended_iterator_last.rs
@@ -24,7 +24,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &'_ Expr<'_>, self_expr: &'_ Exp
         && let Ok(Some(fn_def)) = Instance::try_resolve(cx.tcx, cx.typing_env(), id, args)
         // find the provided definition of Iterator::last
         && let Some(item) = cx.tcx.get_diagnostic_item(sym::Iterator)
-        && let Some(last_def) = cx.tcx.provided_trait_methods(item).find(|m| m.name.as_str() == "last")
+        && let Some(last_def) = cx.tcx.provided_trait_methods(item).find(|m| m.name().as_str() == "last")
         // if the resolved method is the same as the provided definition
         && fn_def.def_id() == last_def.def_id
     {
diff --git a/src/tools/clippy/clippy_lints/src/missing_trait_methods.rs b/src/tools/clippy/clippy_lints/src/missing_trait_methods.rs
index 7ee746365d102..e266c36b6e734 100644
--- a/src/tools/clippy/clippy_lints/src/missing_trait_methods.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_trait_methods.rs
@@ -81,7 +81,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingTraitMethods {
                     cx,
                     MISSING_TRAIT_METHODS,
                     cx.tcx.def_span(item.owner_id),
-                    format!("missing trait method provided by default: `{}`", assoc.name),
+                    format!("missing trait method provided by default: `{}`", assoc.name()),
                     |diag| {
                         diag.span_help(cx.tcx.def_span(assoc.def_id), "implement the method");
                     },
diff --git a/src/tools/clippy/clippy_lints/src/same_name_method.rs b/src/tools/clippy/clippy_lints/src/same_name_method.rs
index ae677e110af27..33815cc3bac1b 100644
--- a/src/tools/clippy/clippy_lints/src/same_name_method.rs
+++ b/src/tools/clippy/clippy_lints/src/same_name_method.rs
@@ -85,7 +85,7 @@ impl<'tcx> LateLintPass<'tcx> for SameNameMethod {
                                 .associated_items(did)
                                 .in_definition_order()
                                 .filter(|assoc_item| assoc_item.is_fn())
-                                .map(|assoc_item| assoc_item.name)
+                                .map(|assoc_item| assoc_item.name())
                                 .collect()
                         } else {
                             BTreeSet::new()
diff --git a/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs b/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
index 2104eb302ab88..0c17cc5d8f667 100644
--- a/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
+++ b/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
@@ -322,7 +322,7 @@ impl UnconditionalRecursion {
                             .in_definition_order()
                             // We're not interested in foreign implementations of the `Default` trait.
                             .find(|item| {
-                                item.is_fn() && item.def_id.is_local() && item.name == kw::Default
+                                item.is_fn() && item.def_id.is_local() && item.name() == kw::Default
                             })
                         && let Some(body_node) = cx.tcx.hir_get_if_local(assoc_item.def_id)
                         && let Some(body_id) = body_node.body_id()

From 1376810d44d62dc7e8146f988e41aa2a9f641cf8 Mon Sep 17 00:00:00 2001
From: Glyn Normington <glyn.normington@gmail.com>
Date: Tue, 15 Apr 2025 02:34:32 +0100
Subject: [PATCH 24/24] Basic tests of MPMC receiver cloning

Ref: https://github.com/rust-lang/rust/issues/126840#issuecomment-2802321146
---
 library/std/tests/sync/mpmc.rs | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/library/std/tests/sync/mpmc.rs b/library/std/tests/sync/mpmc.rs
index 81b92297f76a3..78abcb3bcbe1d 100644
--- a/library/std/tests/sync/mpmc.rs
+++ b/library/std/tests/sync/mpmc.rs
@@ -63,6 +63,24 @@ fn smoke_port_gone() {
     assert!(tx.send(1).is_err());
 }
 
+#[test]
+fn smoke_receiver_clone() {
+    let (tx, rx) = channel::<i32>();
+    let rx2 = rx.clone();
+    drop(rx);
+    tx.send(1).unwrap();
+    assert_eq!(rx2.recv().unwrap(), 1);
+}
+
+#[test]
+fn smoke_receiver_clone_port_gone() {
+    let (tx, rx) = channel::<i32>();
+    let rx2 = rx.clone();
+    drop(rx);
+    drop(rx2);
+    assert!(tx.send(1).is_err());
+}
+
 #[test]
 fn smoke_shared_port_gone() {
     let (tx, rx) = channel::<i32>();
@@ -124,6 +142,18 @@ fn chan_gone_concurrent() {
     while rx.recv().is_ok() {}
 }
 
+#[test]
+fn receiver_cloning() {
+    let (tx, rx) = channel::<i32>();
+    let rx2 = rx.clone();
+
+    tx.send(1).unwrap();
+    tx.send(2).unwrap();
+
+    assert_eq!(rx2.recv(), Ok(1));
+    assert_eq!(rx.recv(), Ok(2));
+}
+
 #[test]
 fn stress() {
     let count = if cfg!(miri) { 100 } else { 10000 };