Rollup of 5 pull requests

compiler/rustc_lint/messages.ftl

@@ -462,6 +462,14 @@ lint_invalid_reference_casting_note_book = for more information, visit <https://
 
 lint_invalid_reference_casting_note_ty_has_interior_mutability = even for types with interior mutability, the only legal way to obtain a mutable pointer from a shared reference is through `UnsafeCell::get`
 
+lint_int_to_ptr_transmutes = transmuting an integer to a pointer creates a pointer without provenance
+    .note = this is dangerous because dereferencing the resulting pointer is undefined behavior
+    .note_exposed_provenance = exposed provenance semantics can be used to create a pointer based on some previously exposed provenance
+    .help_transmute = for more information about transmute, see <https://doc.rust-lang.org/std/mem/fn.transmute.html#transmutation-between-pointers-and-integers>
+    .help_exposed_provenance = for more information about exposed provenance, see <https://doc.rust-lang.org/std/ptr/index.html#exposed-provenance>
+    .suggestion_with_exposed_provenance = use `std::ptr::with_exposed_provenance{$suffix}` instead to use a previously exposed provenance
+    .suggestion_without_provenance_mut = if you truly mean to create a pointer without provenance, use `std::ptr::without_provenance_mut`
+
 lint_legacy_derive_helpers = derive helper attribute is used before it is introduced
     .label = the attribute is introduced here
 

compiler/rustc_lint/src/lifetime_syntax.rs

@@ -214,9 +214,9 @@ impl<T> LifetimeSyntaxCategories<Vec<T>> {
         }
     }
 
-    pub fn flatten(&self) -> impl Iterator<Item = &T> {
-        let Self { hidden, elided, named } = self;
-        [hidden.iter(), elided.iter(), named.iter()].into_iter().flatten()
+    pub fn iter_unnamed(&self) -> impl Iterator<Item = &T> {
+        let Self { hidden, elided, named: _ } = self;
+        [hidden.iter(), elided.iter()].into_iter().flatten()
     }
 }
 
@@ -495,7 +495,7 @@ fn emit_mismatch_diagnostic<'tcx>(
 
     cx.emit_span_lint(
         MISMATCHED_LIFETIME_SYNTAXES,
-        inputs.flatten().copied().collect::<Vec<_>>(),
+        inputs.iter_unnamed().chain(outputs.iter_unnamed()).copied().collect::<Vec<_>>(),
         lints::MismatchedLifetimeSyntaxes { inputs, outputs, suggestions },
     );
 }

compiler/rustc_lint/src/lints.rs

@@ -1,3 +1,5 @@
+// ignore-tidy-filelength
+
 #![allow(rustc::untranslatable_diagnostic)]
 use std::num::NonZero;
 
@@ -1542,6 +1544,48 @@ impl<'a> LintDiagnostic<'a, ()> for DropGlue<'_> {
     }
 }
 
+// transmute.rs
+#[derive(LintDiagnostic)]
+#[diag(lint_int_to_ptr_transmutes)]
+#[note]
+#[note(lint_note_exposed_provenance)]
+#[help(lint_suggestion_without_provenance_mut)]
+#[help(lint_help_transmute)]
+#[help(lint_help_exposed_provenance)]
+pub(crate) struct IntegerToPtrTransmutes<'tcx> {
+    #[subdiagnostic]
+    pub suggestion: IntegerToPtrTransmutesSuggestion<'tcx>,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum IntegerToPtrTransmutesSuggestion<'tcx> {
+    #[multipart_suggestion(
+        lint_suggestion_with_exposed_provenance,
+        applicability = "machine-applicable",
+        style = "verbose"
+    )]
+    ToPtr {
+        dst: Ty<'tcx>,
+        suffix: &'static str,
+        #[suggestion_part(code = "std::ptr::with_exposed_provenance{suffix}::<{dst}>(")]
+        start_call: Span,
+    },
+    #[multipart_suggestion(
+        lint_suggestion_with_exposed_provenance,
+        applicability = "machine-applicable",
+        style = "verbose"
+    )]
+    ToRef {
+        dst: Ty<'tcx>,
+        suffix: &'static str,
+        ref_mutbl: &'static str,
+        #[suggestion_part(
+            code = "&{ref_mutbl}*std::ptr::with_exposed_provenance{suffix}::<{dst}>("
+        )]
+        start_call: Span,
+    },
+}
+
 // types.rs
 #[derive(LintDiagnostic)]
 #[diag(lint_range_endpoint_out_of_range)]

compiler/rustc_lint/src/transmute.rs

@@ -1,3 +1,4 @@
+use rustc_ast::LitKind;
 use rustc_errors::Applicability;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::LocalDefId;
@@ -7,6 +8,7 @@ use rustc_middle::ty::{self, Ty};
 use rustc_session::{declare_lint, impl_lint_pass};
 use rustc_span::sym;
 
+use crate::lints::{IntegerToPtrTransmutes, IntegerToPtrTransmutesSuggestion};
 use crate::{LateContext, LateLintPass};
 
 declare_lint! {
@@ -67,9 +69,44 @@ declare_lint! {
     "detects transmutes that can also be achieved by other operations"
 }
 
+declare_lint! {
+    /// The `integer_to_ptr_transmutes` lint detects integer to pointer
+    /// transmutes where the resulting pointers are undefined behavior to dereference.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn foo(a: usize) -> *const u8 {
+    ///    unsafe {
+    ///        std::mem::transmute::<usize, *const u8>(a)
+    ///    }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Any attempt to use the resulting pointers are undefined behavior as the resulting
+    /// pointers won't have any provenance.
+    ///
+    /// Alternatively, [`std::ptr::with_exposed_provenance`] should be used, as they do not
+    /// carry the provenance requirement. If wanting to create pointers without provenance
+    /// [`std::ptr::without_provenance`] should be used instead.
+    ///
+    /// See [`std::mem::transmute`] in the reference for more details.
+    ///
+    /// [`std::mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
+    /// [`std::ptr::with_exposed_provenance`]: https://doc.rust-lang.org/std/ptr/fn.with_exposed_provenance.html
+    /// [`std::ptr::without_provenance`]: https://doc.rust-lang.org/std/ptr/fn.without_provenance.html
+    pub INTEGER_TO_PTR_TRANSMUTES,
+    Warn,
+    "detects integer to pointer transmutes",
+}
+
 pub(crate) struct CheckTransmutes;
 
-impl_lint_pass!(CheckTransmutes => [PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS, UNNECESSARY_TRANSMUTES]);
+impl_lint_pass!(CheckTransmutes => [PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS, UNNECESSARY_TRANSMUTES, INTEGER_TO_PTR_TRANSMUTES]);
 
 impl<'tcx> LateLintPass<'tcx> for CheckTransmutes {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
@@ -94,9 +131,62 @@ impl<'tcx> LateLintPass<'tcx> for CheckTransmutes {
 
         check_ptr_transmute_in_const(cx, expr, body_owner_def_id, const_context, src, dst);
         check_unnecessary_transmute(cx, expr, callee, arg, const_context, src, dst);
+        check_int_to_ptr_transmute(cx, expr, arg, src, dst);
     }
 }
 
+/// Check for transmutes from integer to pointers (*const/*mut and &/&mut).
+///
+/// Using the resulting pointers would be undefined behavior.
+fn check_int_to_ptr_transmute<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx hir::Expr<'tcx>,
+    arg: &'tcx hir::Expr<'tcx>,
+    src: Ty<'tcx>,
+    dst: Ty<'tcx>,
+) {
+    if !matches!(src.kind(), ty::Uint(_) | ty::Int(_)) {
+        return;
+    }
+    let (ty::Ref(_, inner_ty, mutbl) | ty::RawPtr(inner_ty, mutbl)) = dst.kind() else {
+        return;
+    };
+    // bail-out if the argument is literal 0 as we have other lints for those cases
+    if matches!(arg.kind, hir::ExprKind::Lit(hir::Lit { node: LitKind::Int(v, _), .. }) if v == 0) {
+        return;
+    }
+    // bail-out if the inner type is a ZST
+    let Ok(layout_inner_ty) = cx.tcx.layout_of(cx.typing_env().as_query_input(*inner_ty)) else {
+        return;
+    };
+    if layout_inner_ty.is_1zst() {
+        return;
+    }
+
+    let suffix = if mutbl.is_mut() { "_mut" } else { "" };
+    cx.tcx.emit_node_span_lint(
+        INTEGER_TO_PTR_TRANSMUTES,
+        expr.hir_id,
+        expr.span,
+        IntegerToPtrTransmutes {
+            suggestion: if dst.is_ref() {
+                IntegerToPtrTransmutesSuggestion::ToRef {
+                    dst: *inner_ty,
+                    suffix,
+                    ref_mutbl: mutbl.prefix_str(),
+                    start_call: expr.span.shrink_to_lo().until(arg.span),
+                }
+            } else {
+                IntegerToPtrTransmutesSuggestion::ToPtr {
+                    dst: *inner_ty,
+                    suffix,
+                    start_call: expr.span.shrink_to_lo().until(arg.span),
+                }
+            },
+        },
+    );
+}
+
 /// Check for transmutes that exhibit undefined behavior.
 /// For example, transmuting pointers to integers in a const context.
 ///

library/core/src/ptr/mod.rs

@@ -914,6 +914,7 @@ pub const fn dangling<T>() -> *const T {
 #[must_use]
 #[stable(feature = "strict_provenance", since = "1.84.0")]
 #[rustc_const_stable(feature = "strict_provenance", since = "1.84.0")]
+#[allow(integer_to_ptr_transmutes)] // Expected semantics here.
 pub const fn without_provenance_mut<T>(addr: usize) -> *mut T {
     // An int-to-pointer transmute currently has exactly the intended semantics: it creates a
     // pointer without provenance. Note that this is *not* a stable guarantee about transmute

library/std/src/lib.rs

@@ -15,7 +15,7 @@
 //!
 //! If you already know the name of what you are looking for, the fastest way to
 //! find it is to use the <a href="#" onclick="window.searchState.focus();">search
-//! bar</a> at the top of the page.
+//! button</a> at the top of the page.
 //!
 //! Otherwise, you may want to jump to one of these useful sections:
 //!

library/std/src/sync/lazy_lock.rs

@@ -244,7 +244,11 @@ impl<T, F: FnOnce() -> T> LazyLock<T, F> {
     #[inline]
     #[stable(feature = "lazy_cell", since = "1.80.0")]
     pub fn force(this: &LazyLock<T, F>) -> &T {
-        this.once.call_once(|| {
+        this.once.call_once_force(|state| {
+            if state.is_poisoned() {
+                panic_poisoned();
+            }
+
             // SAFETY: `call_once` only runs this closure once, ever.
             let data = unsafe { &mut *this.data.get() };
             let f = unsafe { ManuallyDrop::take(&mut data.f) };
@@ -257,8 +261,7 @@ impl<T, F: FnOnce() -> T> LazyLock<T, F> {
         // * the closure was called and initialized `value`.
         // * the closure was called and panicked, so this point is never reached.
         // * the closure was not called, but a previous call initialized `value`.
-        // * the closure was not called because the Once is poisoned, so this point
-        //   is never reached.
+        // * the closure was not called because the Once is poisoned, which we handled above.
         // So `value` has definitely been initialized and will not be modified again.
         unsafe { &*(*this.data.get()).value }
     }

library/std/tests/sync/lazy_lock.rs

@@ -33,16 +33,6 @@ fn lazy_default() {
     assert_eq!(CALLED.load(SeqCst), 1);
 }
 
-#[test]
-#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn lazy_poisoning() {
-    let x: LazyCell<String> = LazyCell::new(|| panic!("kaboom"));
-    for _ in 0..2 {
-        let res = panic::catch_unwind(panic::AssertUnwindSafe(|| x.len()));
-        assert!(res.is_err());
-    }
-}
-
 #[test]
 #[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
 fn sync_lazy_new() {
@@ -123,16 +113,6 @@ fn static_sync_lazy_via_fn() {
     assert_eq!(xs(), &vec![1, 2, 3]);
 }
 
-#[test]
-#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn sync_lazy_poisoning() {
-    let x: LazyLock<String> = LazyLock::new(|| panic!("kaboom"));
-    for _ in 0..2 {
-        let res = panic::catch_unwind(|| x.len());
-        assert!(res.is_err());
-    }
-}
-
 // Check that we can infer `T` from closure's type.
 #[test]
 fn lazy_type_inference() {
@@ -145,17 +125,6 @@ fn is_sync_send() {
     assert_traits::<LazyLock<String>>();
 }
 
-#[test]
-#[should_panic = "has previously been poisoned"]
-fn lazy_force_mut_panic() {
-    let mut lazy = LazyLock::<String>::new(|| panic!());
-    panic::catch_unwind(panic::AssertUnwindSafe(|| {
-        let _ = LazyLock::force_mut(&mut lazy);
-    }))
-    .unwrap_err();
-    let _ = &*lazy;
-}
-
 #[test]
 fn lazy_force_mut() {
     let s = "abc".to_owned();
@@ -165,3 +134,56 @@ fn lazy_force_mut() {
     p.clear();
     LazyLock::force_mut(&mut lazy);
 }
+
+#[test]
+#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
+fn lazy_poisoning() {
+    let x: LazyCell<String> = LazyCell::new(|| panic!("kaboom"));
+    for _ in 0..2 {
+        let res = panic::catch_unwind(panic::AssertUnwindSafe(|| x.len()));
+        assert!(res.is_err());
+    }
+}
+
+/// Verifies that when a `LazyLock` is poisoned, it panics with the correct error message ("LazyLock
+/// instance has previously been poisoned") instead of the underlying `Once` error message.
+#[test]
+#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
+#[should_panic(expected = "LazyLock instance has previously been poisoned")]
+fn lazy_lock_deref_panic() {
+    let lazy: LazyLock<String> = LazyLock::new(|| panic!("initialization failed"));
+
+    // First access will panic during initialization.
+    let _ = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        let _ = &*lazy;
+    }));
+
+    // Second access should panic with the poisoned message.
+    let _ = &*lazy;
+}
+
+#[test]
+#[should_panic(expected = "LazyLock instance has previously been poisoned")]
+fn lazy_lock_deref_mut_panic() {
+    let mut lazy: LazyLock<String> = LazyLock::new(|| panic!("initialization failed"));
+
+    // First access will panic during initialization.
+    let _ = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        let _ = LazyLock::force_mut(&mut lazy);
+    }));
+
+    // Second access should panic with the poisoned message.
+    let _ = &*lazy;
+}
+
+/// Verifies that when the initialization closure panics with a custom message, that message is
+/// preserved and not overridden by `LazyLock`.
+#[test]
+#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
+#[should_panic(expected = "custom panic message from closure")]
+fn lazy_lock_preserves_closure_panic_message() {
+    let lazy: LazyLock<String> = LazyLock::new(|| panic!("custom panic message from closure"));
+
+    // This should panic with the original message from the closure.
+    let _ = &*lazy;
+}

src/doc/rustc-dev-guide/.github/workflows/rustc-pull.yml

@@ -3,8 +3,8 @@ name: rustc-pull
 on:
   workflow_dispatch:
   schedule:
-    # Run at 04:00 UTC every Monday and Thursday
-    - cron: '0 4 * * 1,4'
+    # Run at 04:00 UTC every Monday
+    - cron: '0 4 * * 1'
 
 jobs:
   pull:

src/doc/rustc-dev-guide/rust-version

@@ -1 +1 @@
-6bcdcc73bd11568fd85f5a38b58e1eda054ad1cd
+425a9c0a0e365c0b8c6cfd00c2ded83a73bed9a0

src/doc/rustc-dev-guide/src/about-this-guide.md

@@ -74,7 +74,6 @@ You might also find the following sites useful:
   of the team procedures, active working groups, and the team calendar.
 - [std-dev-guide] -- a similar guide for developing the standard library.
 - [The t-compiler zulip][z]
-- `#contribute` and `#wg-rustup` on [Discord](https://discord.gg/rust-lang).
 - The [Rust Internals forum][rif], a place to ask questions and
   discuss Rust's internals
 - The [Rust reference][rr], even though it doesn't specifically talk about

src/doc/rustc-dev-guide/src/diagnostics/error-codes.md

@@ -20,7 +20,7 @@ explanations should help users understand why their code cannot be accepted by
 the compiler. Rust prides itself on helpful error messages and long-form
 explanations are no exception. However, before error explanations are
 overhauled[^new-explanations] it is a bit open as to how exactly they should be
-written, as always: ask your reviewer or ask around on the Rust Discord or Zulip.
+written, as always: ask your reviewer or ask around on the Rust Zulip.
 
 [^new-explanations]: See the draft RFC [here][new-explanations-rfc].