diff --git a/tests/ui/README.md b/tests/ui/README.md
index 25e870fd8f188..ca9f89f002ee4 100644
--- a/tests/ui/README.md
+++ b/tests/ui/README.md
@@ -256,6 +256,10 @@ Some traits' implementation must be compared with their definition, checking for
 
 This subdirectory is *not* intended comparison traits (`PartialEq`, `Eq`, `PartialOrd`, `Ord`).
 
+## `tests/ui/compile-flags/`
+
+Tests for compile flags.
+
 ## `tests/ui/compiletest-self-test/`: compiletest "meta" tests
 
 Meta test suite of the test harness `compiletest` itself.
@@ -548,6 +552,8 @@ A broad directory for tests on expressions.
 
 Tests on the `extern` keyword and `extern` blocks and functions.
 
+**FIXME**: Merge with `tests/ui/abi/extern`.
+
 ## `tests/ui/extern-flag/`: `--extern` command line flag
 
 Tests for the `--extern` CLI flag.
@@ -556,6 +562,12 @@ Tests for the `--extern` CLI flag.
 
 Tests on feature-gating, and the `#![feature(..)]` mechanism itself.
 
+## `tests/ui/ffi/`: Foreign Function Interface
+
+Tests for the `std::ffi` module.
+
+See [`std::ffi`](https://doc.rust-lang.org/std/ffi/index.html)
+
 ## `tests/ui/ffi-attrs/`: `#![feature(ffi_const, ffi_pure)]`
 
 The `#[ffi_const]` and `#[ffi_pure]` attributes applies clang's `const` and `pure` attributes to foreign functions declarations, respectively. These attributes are the core element of the tests in this category.
@@ -733,15 +745,9 @@ Various tests related to rejecting invalid inputs.
 
 **FIXME**: This is rather uninformative, possibly rehome into more meaningful directories.
 
-## `tests/ui/invalid-compile-flags/`
-
-Tests for checking that invalid usage of compiler flags are rejected.
-
-## `tests/ui/io-checks/`
-
-Contains a single test. The test tries to output a file into an invalid directory with `-o`, then checks that the result is an error, not an internal compiler error.
+## `tests/ui/io-checks/`: Input Output
 
-**FIXME**: Rehome to invalid compiler flags maybe.
+Tests for I/O related behaviour, covering stdout/stderr handling and error propagation.
 
 ## `tests/ui/issues/`: Tests directly related to GitHub issues
 
diff --git a/tests/ui/issues/issue-46472.rs b/tests/ui/borrowck/return-ref-to-temporary.rs
similarity index 55%
rename from tests/ui/issues/issue-46472.rs
rename to tests/ui/borrowck/return-ref-to-temporary.rs
index b9e20e8dbcb5f..90609b8d6da6d 100644
--- a/tests/ui/issues/issue-46472.rs
+++ b/tests/ui/borrowck/return-ref-to-temporary.rs
@@ -1,6 +1,7 @@
+//! regression test for issue https://github.com/rust-lang/rust/issues/46472
 fn bar<'a>() -> &'a mut u32 {
     &mut 4
     //~^ ERROR cannot return reference to temporary value [E0515]
 }
 
-fn main() { }
+fn main() {}
diff --git a/tests/ui/issues/issue-46472.stderr b/tests/ui/borrowck/return-ref-to-temporary.stderr
similarity index 88%
rename from tests/ui/issues/issue-46472.stderr
rename to tests/ui/borrowck/return-ref-to-temporary.stderr
index 6115da28cc91c..85faf0a9e3758 100644
--- a/tests/ui/issues/issue-46472.stderr
+++ b/tests/ui/borrowck/return-ref-to-temporary.stderr
@@ -1,5 +1,5 @@
 error[E0515]: cannot return reference to temporary value
-  --> $DIR/issue-46472.rs:2:5
+  --> $DIR/return-ref-to-temporary.rs:3:5
    |
 LL |     &mut 4
    |     ^^^^^-
diff --git a/tests/ui/issues/issue-19499.rs b/tests/ui/closures/closure-upvar-trait-caching.rs
similarity index 85%
rename from tests/ui/issues/issue-19499.rs
rename to tests/ui/closures/closure-upvar-trait-caching.rs
index d2a6862e05c4f..82588631c99c3 100644
--- a/tests/ui/issues/issue-19499.rs
+++ b/tests/ui/closures/closure-upvar-trait-caching.rs
@@ -7,8 +7,9 @@
 // reasonable examples) let to ambiguity errors about not being able
 // to infer sufficient type information.
 
-
 fn main() {
     let n = 0;
-    let it = Some(1_usize).into_iter().inspect(|_| {n;});
+    let it = Some(1_usize).into_iter().inspect(|_| {
+        n;
+    });
 }
diff --git a/tests/ui/closures/nested-closure-call.rs b/tests/ui/closures/nested-closure-call.rs
new file mode 100644
index 0000000000000..9d0860167a1ac
--- /dev/null
+++ b/tests/ui/closures/nested-closure-call.rs
@@ -0,0 +1,5 @@
+//! regression test for https://github.com/rust-lang/rust/issues/24779
+//@ run-pass
+fn main() {
+    assert_eq!((|| || 42)()(), 42);
+}
diff --git a/tests/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADFLAGS.stderr b/tests/ui/compile-flags/invalid/branch-protection-missing-pac-ret.BADFLAGS.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADFLAGS.stderr
rename to tests/ui/compile-flags/invalid/branch-protection-missing-pac-ret.BADFLAGS.stderr
diff --git a/tests/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADFLAGSPC.stderr b/tests/ui/compile-flags/invalid/branch-protection-missing-pac-ret.BADFLAGSPC.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADFLAGSPC.stderr
rename to tests/ui/compile-flags/invalid/branch-protection-missing-pac-ret.BADFLAGSPC.stderr
diff --git a/tests/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADTARGET.stderr b/tests/ui/compile-flags/invalid/branch-protection-missing-pac-ret.BADTARGET.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADTARGET.stderr
rename to tests/ui/compile-flags/invalid/branch-protection-missing-pac-ret.BADTARGET.stderr
diff --git a/tests/ui/invalid-compile-flags/branch-protection-missing-pac-ret.rs b/tests/ui/compile-flags/invalid/branch-protection-missing-pac-ret.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/branch-protection-missing-pac-ret.rs
rename to tests/ui/compile-flags/invalid/branch-protection-missing-pac-ret.rs
diff --git a/tests/ui/invalid-compile-flags/codegen-option-without-group.rs b/tests/ui/compile-flags/invalid/codegen-option-without-group.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/codegen-option-without-group.rs
rename to tests/ui/compile-flags/invalid/codegen-option-without-group.rs
diff --git a/tests/ui/invalid-compile-flags/codegen-option-without-group.stderr b/tests/ui/compile-flags/invalid/codegen-option-without-group.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/codegen-option-without-group.stderr
rename to tests/ui/compile-flags/invalid/codegen-option-without-group.stderr
diff --git a/tests/ui/invalid-compile-flags/crate-type-flag.empty_crate_type.stderr b/tests/ui/compile-flags/invalid/crate-type-flag.empty_crate_type.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/crate-type-flag.empty_crate_type.stderr
rename to tests/ui/compile-flags/invalid/crate-type-flag.empty_crate_type.stderr
diff --git a/tests/ui/invalid-compile-flags/crate-type-flag.proc_underscore_macro.stderr b/tests/ui/compile-flags/invalid/crate-type-flag.proc_underscore_macro.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/crate-type-flag.proc_underscore_macro.stderr
rename to tests/ui/compile-flags/invalid/crate-type-flag.proc_underscore_macro.stderr
diff --git a/tests/ui/invalid-compile-flags/crate-type-flag.rs b/tests/ui/compile-flags/invalid/crate-type-flag.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/crate-type-flag.rs
rename to tests/ui/compile-flags/invalid/crate-type-flag.rs
diff --git a/tests/ui/invalid-compile-flags/crate-type-flag.unknown.stderr b/tests/ui/compile-flags/invalid/crate-type-flag.unknown.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/crate-type-flag.unknown.stderr
rename to tests/ui/compile-flags/invalid/crate-type-flag.unknown.stderr
diff --git a/tests/ui/invalid-compile-flags/debug-option-without-group.rs b/tests/ui/compile-flags/invalid/debug-option-without-group.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/debug-option-without-group.rs
rename to tests/ui/compile-flags/invalid/debug-option-without-group.rs
diff --git a/tests/ui/invalid-compile-flags/debug-option-without-group.stderr b/tests/ui/compile-flags/invalid/debug-option-without-group.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/debug-option-without-group.stderr
rename to tests/ui/compile-flags/invalid/debug-option-without-group.stderr
diff --git a/tests/ui/invalid-compile-flags/emit-output-types-without-args.rs b/tests/ui/compile-flags/invalid/emit-output-types-without-args.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/emit-output-types-without-args.rs
rename to tests/ui/compile-flags/invalid/emit-output-types-without-args.rs
diff --git a/tests/ui/invalid-compile-flags/emit-output-types-without-args.stderr b/tests/ui/compile-flags/invalid/emit-output-types-without-args.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/emit-output-types-without-args.stderr
rename to tests/ui/compile-flags/invalid/emit-output-types-without-args.stderr
diff --git a/tests/ui/invalid-compile-flags/function-return/requires-x86-or-x86_64.aarch64.stderr b/tests/ui/compile-flags/invalid/function-return/requires-x86-or-x86_64.aarch64.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/function-return/requires-x86-or-x86_64.aarch64.stderr
rename to tests/ui/compile-flags/invalid/function-return/requires-x86-or-x86_64.aarch64.stderr
diff --git a/tests/ui/invalid-compile-flags/function-return/requires-x86-or-x86_64.rs b/tests/ui/compile-flags/invalid/function-return/requires-x86-or-x86_64.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/function-return/requires-x86-or-x86_64.rs
rename to tests/ui/compile-flags/invalid/function-return/requires-x86-or-x86_64.rs
diff --git a/tests/ui/invalid-compile-flags/function-return/thunk-extern-requires-non-large-code-model.large.stderr b/tests/ui/compile-flags/invalid/function-return/thunk-extern-requires-non-large-code-model.large.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/function-return/thunk-extern-requires-non-large-code-model.large.stderr
rename to tests/ui/compile-flags/invalid/function-return/thunk-extern-requires-non-large-code-model.large.stderr
diff --git a/tests/ui/invalid-compile-flags/function-return/thunk-extern-requires-non-large-code-model.rs b/tests/ui/compile-flags/invalid/function-return/thunk-extern-requires-non-large-code-model.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/function-return/thunk-extern-requires-non-large-code-model.rs
rename to tests/ui/compile-flags/invalid/function-return/thunk-extern-requires-non-large-code-model.rs
diff --git a/tests/ui/invalid-compile-flags/indirect-branch-cs-prefix/requires-x86-or-x86_64.aarch64.stderr b/tests/ui/compile-flags/invalid/indirect-branch-cs-prefix/requires-x86-or-x86_64.aarch64.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/indirect-branch-cs-prefix/requires-x86-or-x86_64.aarch64.stderr
rename to tests/ui/compile-flags/invalid/indirect-branch-cs-prefix/requires-x86-or-x86_64.aarch64.stderr
diff --git a/tests/ui/invalid-compile-flags/indirect-branch-cs-prefix/requires-x86-or-x86_64.rs b/tests/ui/compile-flags/invalid/indirect-branch-cs-prefix/requires-x86-or-x86_64.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/indirect-branch-cs-prefix/requires-x86-or-x86_64.rs
rename to tests/ui/compile-flags/invalid/indirect-branch-cs-prefix/requires-x86-or-x86_64.rs
diff --git a/tests/ui/invalid-compile-flags/invalid-llvm-passes.rs b/tests/ui/compile-flags/invalid/invalid-llvm-passes.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/invalid-llvm-passes.rs
rename to tests/ui/compile-flags/invalid/invalid-llvm-passes.rs
diff --git a/tests/ui/invalid-compile-flags/invalid-llvm-passes.stderr b/tests/ui/compile-flags/invalid/invalid-llvm-passes.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/invalid-llvm-passes.stderr
rename to tests/ui/compile-flags/invalid/invalid-llvm-passes.stderr
diff --git a/tests/ui/invalid-compile-flags/need-crate-arg-ignore-tidy$x.rs b/tests/ui/compile-flags/invalid/need-crate-arg-ignore-tidy$x.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/need-crate-arg-ignore-tidy$x.rs
rename to tests/ui/compile-flags/invalid/need-crate-arg-ignore-tidy$x.rs
diff --git a/tests/ui/invalid-compile-flags/need-crate-arg-ignore-tidy$x.stderr b/tests/ui/compile-flags/invalid/need-crate-arg-ignore-tidy$x.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/need-crate-arg-ignore-tidy$x.stderr
rename to tests/ui/compile-flags/invalid/need-crate-arg-ignore-tidy$x.stderr
diff --git a/tests/ui/invalid-compile-flags/print-crate-name-request-malformed-crate-name.rs b/tests/ui/compile-flags/invalid/print-crate-name-request-malformed-crate-name.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-crate-name-request-malformed-crate-name.rs
rename to tests/ui/compile-flags/invalid/print-crate-name-request-malformed-crate-name.rs
diff --git a/tests/ui/invalid-compile-flags/print-crate-name-request-malformed-crate-name.stderr b/tests/ui/compile-flags/invalid/print-crate-name-request-malformed-crate-name.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-crate-name-request-malformed-crate-name.stderr
rename to tests/ui/compile-flags/invalid/print-crate-name-request-malformed-crate-name.stderr
diff --git a/tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name-1.rs b/tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name-1.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name-1.rs
rename to tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name-1.rs
diff --git a/tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name-1.stderr b/tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name-1.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name-1.stderr
rename to tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name-1.stderr
diff --git a/tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name-2.rs b/tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name-2.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name-2.rs
rename to tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name-2.rs
diff --git a/tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name-2.stderr b/tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name-2.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name-2.stderr
rename to tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name-2.stderr
diff --git a/tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name.rs b/tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name.rs
rename to tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name.rs
diff --git a/tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name.stderr b/tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-file-names-request-malformed-crate-name.stderr
rename to tests/ui/compile-flags/invalid/print-file-names-request-malformed-crate-name.stderr
diff --git a/tests/ui/invalid-compile-flags/print-without-arg.rs b/tests/ui/compile-flags/invalid/print-without-arg.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-without-arg.rs
rename to tests/ui/compile-flags/invalid/print-without-arg.rs
diff --git a/tests/ui/invalid-compile-flags/print-without-arg.stderr b/tests/ui/compile-flags/invalid/print-without-arg.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/print-without-arg.stderr
rename to tests/ui/compile-flags/invalid/print-without-arg.stderr
diff --git a/tests/ui/invalid-compile-flags/print.rs b/tests/ui/compile-flags/invalid/print.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/print.rs
rename to tests/ui/compile-flags/invalid/print.rs
diff --git a/tests/ui/invalid-compile-flags/print.stderr b/tests/ui/compile-flags/invalid/print.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/print.stderr
rename to tests/ui/compile-flags/invalid/print.stderr
diff --git a/tests/ui/invalid-compile-flags/reg-struct-return/requires-x86.aarch64.stderr b/tests/ui/compile-flags/invalid/reg-struct-return/requires-x86.aarch64.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/reg-struct-return/requires-x86.aarch64.stderr
rename to tests/ui/compile-flags/invalid/reg-struct-return/requires-x86.aarch64.stderr
diff --git a/tests/ui/invalid-compile-flags/reg-struct-return/requires-x86.rs b/tests/ui/compile-flags/invalid/reg-struct-return/requires-x86.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/reg-struct-return/requires-x86.rs
rename to tests/ui/compile-flags/invalid/reg-struct-return/requires-x86.rs
diff --git a/tests/ui/invalid-compile-flags/reg-struct-return/requires-x86.x86_64.stderr b/tests/ui/compile-flags/invalid/reg-struct-return/requires-x86.x86_64.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/reg-struct-return/requires-x86.x86_64.stderr
rename to tests/ui/compile-flags/invalid/reg-struct-return/requires-x86.x86_64.stderr
diff --git a/tests/ui/invalid-compile-flags/regparm/regparm-valid-values.regparm4.stderr b/tests/ui/compile-flags/invalid/regparm/regparm-valid-values.regparm4.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/regparm/regparm-valid-values.regparm4.stderr
rename to tests/ui/compile-flags/invalid/regparm/regparm-valid-values.regparm4.stderr
diff --git a/tests/ui/invalid-compile-flags/regparm/regparm-valid-values.rs b/tests/ui/compile-flags/invalid/regparm/regparm-valid-values.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/regparm/regparm-valid-values.rs
rename to tests/ui/compile-flags/invalid/regparm/regparm-valid-values.rs
diff --git a/tests/ui/invalid-compile-flags/regparm/requires-x86.aarch64.stderr b/tests/ui/compile-flags/invalid/regparm/requires-x86.aarch64.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/regparm/requires-x86.aarch64.stderr
rename to tests/ui/compile-flags/invalid/regparm/requires-x86.aarch64.stderr
diff --git a/tests/ui/invalid-compile-flags/regparm/requires-x86.rs b/tests/ui/compile-flags/invalid/regparm/requires-x86.rs
similarity index 100%
rename from tests/ui/invalid-compile-flags/regparm/requires-x86.rs
rename to tests/ui/compile-flags/invalid/regparm/requires-x86.rs
diff --git a/tests/ui/invalid-compile-flags/regparm/requires-x86.x86_64.stderr b/tests/ui/compile-flags/invalid/regparm/requires-x86.x86_64.stderr
similarity index 100%
rename from tests/ui/invalid-compile-flags/regparm/requires-x86.x86_64.stderr
rename to tests/ui/compile-flags/invalid/regparm/requires-x86.x86_64.stderr
diff --git a/tests/ui/issues/issue-24945-repeat-dash-opts.rs b/tests/ui/compile-flags/run-pass/repeated-debug-opt-flags.rs
similarity index 72%
rename from tests/ui/issues/issue-24945-repeat-dash-opts.rs
rename to tests/ui/compile-flags/run-pass/repeated-debug-opt-flags.rs
index 5d8044b0a1a06..d584ec9fd280d 100644
--- a/tests/ui/issues/issue-24945-repeat-dash-opts.rs
+++ b/tests/ui/compile-flags/run-pass/repeated-debug-opt-flags.rs
@@ -1,3 +1,4 @@
+//! regression test for https://github.com/rust-lang/rust/issues/24945
 //@ run-pass
 // This test is just checking that we continue to accept `-g -g -O -O`
 // as options to the compiler.
diff --git a/tests/ui/enum/enum-variant-no-field.rs b/tests/ui/enum/enum-variant-no-field.rs
new file mode 100644
index 0000000000000..a69766b7c48d0
--- /dev/null
+++ b/tests/ui/enum/enum-variant-no-field.rs
@@ -0,0 +1,9 @@
+//! regression test for https://github.com/rust-lang/rust/issues/23253
+enum Foo {
+    Bar,
+}
+
+fn main() {
+    Foo::Bar.a;
+    //~^ ERROR no field `a` on type `Foo`
+}
diff --git a/tests/ui/issues/issue-23253.stderr b/tests/ui/enum/enum-variant-no-field.stderr
similarity index 83%
rename from tests/ui/issues/issue-23253.stderr
rename to tests/ui/enum/enum-variant-no-field.stderr
index ec7696909e725..4d02bf8761891 100644
--- a/tests/ui/issues/issue-23253.stderr
+++ b/tests/ui/enum/enum-variant-no-field.stderr
@@ -1,5 +1,5 @@
 error[E0609]: no field `a` on type `Foo`
-  --> $DIR/issue-23253.rs:4:14
+  --> $DIR/enum-variant-no-field.rs:7:14
    |
 LL |     Foo::Bar.a;
    |              ^ unknown field
diff --git a/tests/ui/issues/issue-50442.rs b/tests/ui/enum/enum-with-uninhabited-variant.rs
similarity index 58%
rename from tests/ui/issues/issue-50442.rs
rename to tests/ui/enum/enum-with-uninhabited-variant.rs
index 70c764f33ddf9..8dfa492e6ea5c 100644
--- a/tests/ui/issues/issue-50442.rs
+++ b/tests/ui/enum/enum-with-uninhabited-variant.rs
@@ -1,3 +1,4 @@
+//! regression test for issue https://github.com/rust-lang/rust/issues/50442
 //@ run-pass
 #![allow(dead_code)]
 enum Void {}
@@ -5,7 +6,7 @@ enum Void {}
 enum Foo {
     A(i32),
     B(Void),
-    C(i32)
+    C(i32),
 }
 
 fn main() {
diff --git a/tests/ui/expr/return-in-block-tuple.rs b/tests/ui/expr/return-in-block-tuple.rs
new file mode 100644
index 0000000000000..2b3a59f21412f
--- /dev/null
+++ b/tests/ui/expr/return-in-block-tuple.rs
@@ -0,0 +1,7 @@
+//! regression test for https://github.com/rust-lang/rust/issues/18110
+//@ run-pass
+#![allow(unreachable_code)]
+
+fn main() {
+    ({ return },);
+}
diff --git a/tests/ui/issues/issue-19398.rs b/tests/ui/extern/extern-rust-trait-method.rs
similarity index 66%
rename from tests/ui/issues/issue-19398.rs
rename to tests/ui/extern/extern-rust-trait-method.rs
index 473e43650c2c5..d71e5a8b6d532 100644
--- a/tests/ui/issues/issue-19398.rs
+++ b/tests/ui/extern/extern-rust-trait-method.rs
@@ -1,3 +1,4 @@
+//! Regression test for https://github.com/rust-lang/rust/issues/19398
 //@ check-pass
 
 trait T {
diff --git a/tests/ui/issues/issue-3656.rs b/tests/ui/ffi/ffi-struct-size-alignment.rs
similarity index 100%
rename from tests/ui/issues/issue-3656.rs
rename to tests/ui/ffi/ffi-struct-size-alignment.rs
diff --git a/tests/ui/fmt/println-float.rs b/tests/ui/fmt/println-float.rs
new file mode 100644
index 0000000000000..3adb0b4343496
--- /dev/null
+++ b/tests/ui/fmt/println-float.rs
@@ -0,0 +1,5 @@
+//! regression test for https://github.com/rust-lang/rust/issues/11382
+//@ run-pass
+fn main() {
+    println!("{}", 1.2);
+}
diff --git a/tests/ui/indexing/ref-array-indexing.rs b/tests/ui/indexing/ref-array-indexing.rs
new file mode 100644
index 0000000000000..302255798df2d
--- /dev/null
+++ b/tests/ui/indexing/ref-array-indexing.rs
@@ -0,0 +1,6 @@
+//! regression test for https://github.com/rust-lang/rust/issues/43205
+//@ run-pass
+fn main() {
+    let _ = &&[()][0];
+    println!("{:?}", &[(), ()][1]);
+}
diff --git a/tests/ui/issues/issue-10656.rs b/tests/ui/issues/issue-10656.rs
deleted file mode 100644
index 250c4bc442f98..0000000000000
--- a/tests/ui/issues/issue-10656.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-#![deny(missing_docs)]
-#![crate_type="lib"]
-//~^^ ERROR missing documentation for the crate
diff --git a/tests/ui/issues/issue-11382.rs b/tests/ui/issues/issue-11382.rs
deleted file mode 100644
index 18c8c756f32e3..0000000000000
--- a/tests/ui/issues/issue-11382.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-//@ run-pass
-fn main() {
-    println!("{}", 1.2);
-}
diff --git a/tests/ui/issues/issue-17001.rs b/tests/ui/issues/issue-17001.rs
deleted file mode 100644
index 68cb2865fdc82..0000000000000
--- a/tests/ui/issues/issue-17001.rs
+++ /dev/null
@@ -1,5 +0,0 @@
-mod foo {}
-
-fn main() {
-    let p = foo { x: () }; //~ ERROR expected struct, variant or union type, found module `foo`
-}
diff --git a/tests/ui/issues/issue-17450.rs b/tests/ui/issues/issue-17450.rs
deleted file mode 100644
index d8b20169ee0c4..0000000000000
--- a/tests/ui/issues/issue-17450.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-//@ build-pass
-#![allow(dead_code, warnings)]
-
-static mut x: isize = 3;
-static mut y: isize = unsafe { x };
-
-fn main() {}
diff --git a/tests/ui/issues/issue-18110.rs b/tests/ui/issues/issue-18110.rs
deleted file mode 100644
index 6d563a5bae1c9..0000000000000
--- a/tests/ui/issues/issue-18110.rs
+++ /dev/null
@@ -1,6 +0,0 @@
-//@ run-pass
-#![allow(unreachable_code)]
-
-fn main() {
-    ({return},);
-}
diff --git a/tests/ui/issues/issue-18159.rs b/tests/ui/issues/issue-18159.rs
deleted file mode 100644
index bd347d6329846..0000000000000
--- a/tests/ui/issues/issue-18159.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-fn main() {
-    let x; //~ ERROR type annotations needed
-}
diff --git a/tests/ui/issues/issue-18532.rs b/tests/ui/issues/issue-18532.rs
deleted file mode 100644
index 31fd87961dc9f..0000000000000
--- a/tests/ui/issues/issue-18532.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-// Test that overloaded call parameter checking does not ICE
-// when a type error or unconstrained type variable propagates
-// into it.
-
-fn main() {
-    (return)((),()); //~ ERROR expected function, found `!`
-}
diff --git a/tests/ui/issues/issue-20772.rs b/tests/ui/issues/issue-20772.rs
deleted file mode 100644
index 1500bc831528a..0000000000000
--- a/tests/ui/issues/issue-20772.rs
+++ /dev/null
@@ -1,5 +0,0 @@
-trait T : Iterator<Item=Self::Item>
-//~^ ERROR cycle detected
-{}
-
-fn main() {}
diff --git a/tests/ui/issues/issue-21177.rs b/tests/ui/issues/issue-21177.rs
deleted file mode 100644
index 258e362d1317c..0000000000000
--- a/tests/ui/issues/issue-21177.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-trait Trait {
-    type A;
-    type B;
-}
-
-fn foo<T: Trait<A = T::B>>() { }
-//~^ ERROR cycle detected
-
-fn main() { }
diff --git a/tests/ui/issues/issue-21291.rs b/tests/ui/issues/issue-21291.rs
deleted file mode 100644
index 06f50ac6996df..0000000000000
--- a/tests/ui/issues/issue-21291.rs
+++ /dev/null
@@ -1,10 +0,0 @@
-//@ run-pass
-//@ needs-threads
-
-// Regression test for unwrapping the result of `join`, issue #21291
-
-use std::thread;
-
-fn main() {
-    thread::spawn(|| {}).join().unwrap()
-}
diff --git a/tests/ui/issues/issue-21449.rs b/tests/ui/issues/issue-21449.rs
deleted file mode 100644
index 00ce2b7fffa88..0000000000000
--- a/tests/ui/issues/issue-21449.rs
+++ /dev/null
@@ -1,6 +0,0 @@
-mod MyMod {}
-
-fn main() {
-    let myVar = MyMod { T: 0 };
-    //~^ ERROR expected struct, variant or union type, found module `MyMod`
-}
diff --git a/tests/ui/issues/issue-21449.stderr b/tests/ui/issues/issue-21449.stderr
deleted file mode 100644
index cd1059d48993a..0000000000000
--- a/tests/ui/issues/issue-21449.stderr
+++ /dev/null
@@ -1,9 +0,0 @@
-error[E0574]: expected struct, variant or union type, found module `MyMod`
-  --> $DIR/issue-21449.rs:4:17
-   |
-LL |     let myVar = MyMod { T: 0 };
-   |                 ^^^^^ not a struct, variant or union type
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0574`.
diff --git a/tests/ui/issues/issue-23189.rs b/tests/ui/issues/issue-23189.rs
deleted file mode 100644
index e5526357cb0ef..0000000000000
--- a/tests/ui/issues/issue-23189.rs
+++ /dev/null
@@ -1,5 +0,0 @@
-mod module {}
-
-fn main() {
-    let _ = module { x: 0 }; //~ERROR expected struct
-}
diff --git a/tests/ui/issues/issue-23189.stderr b/tests/ui/issues/issue-23189.stderr
deleted file mode 100644
index 37d778dc992eb..0000000000000
--- a/tests/ui/issues/issue-23189.stderr
+++ /dev/null
@@ -1,9 +0,0 @@
-error[E0574]: expected struct, variant or union type, found module `module`
-  --> $DIR/issue-23189.rs:4:13
-   |
-LL |     let _ = module { x: 0 };
-   |             ^^^^^^ not a struct, variant or union type
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0574`.
diff --git a/tests/ui/issues/issue-23253.rs b/tests/ui/issues/issue-23253.rs
deleted file mode 100644
index b285cb81ee230..0000000000000
--- a/tests/ui/issues/issue-23253.rs
+++ /dev/null
@@ -1,6 +0,0 @@
-enum Foo { Bar }
-
-fn main() {
-    Foo::Bar.a;
-    //~^ ERROR no field `a` on type `Foo`
-}
diff --git a/tests/ui/issues/issue-24779.rs b/tests/ui/issues/issue-24779.rs
deleted file mode 100644
index f371828606c4b..0000000000000
--- a/tests/ui/issues/issue-24779.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-//@ run-pass
-fn main() {
-    assert_eq!((||||42)()(), 42);
-}
diff --git a/tests/ui/issues/issue-43205.rs b/tests/ui/issues/issue-43205.rs
deleted file mode 100644
index 9f54d4258bf1d..0000000000000
--- a/tests/ui/issues/issue-43205.rs
+++ /dev/null
@@ -1,5 +0,0 @@
-//@ run-pass
-fn main() {
-   let _ = &&[()][0];
-   println!("{:?}", &[(),()][1]);
-}
diff --git a/tests/ui/issues/issue-4968.rs b/tests/ui/issues/issue-4968.rs
deleted file mode 100644
index 08539d6debd82..0000000000000
--- a/tests/ui/issues/issue-4968.rs
+++ /dev/null
@@ -1,12 +0,0 @@
-// Regression test for issue #4968
-
-//@ dont-require-annotations: NOTE
-
-const A: (isize,isize) = (4,2);
-fn main() {
-    match 42 { A => () }
-    //~^ ERROR mismatched types
-    //~| NOTE expected type `{integer}`
-    //~| NOTE found tuple `(isize, isize)`
-    //~| NOTE expected integer, found `(isize, isize)`
-}
diff --git a/tests/ui/issues/issue-4968.stderr b/tests/ui/issues/issue-4968.stderr
deleted file mode 100644
index 2c1e1d7bfe5a1..0000000000000
--- a/tests/ui/issues/issue-4968.stderr
+++ /dev/null
@@ -1,20 +0,0 @@
-error[E0308]: mismatched types
-  --> $DIR/issue-4968.rs:7:16
-   |
-LL | const A: (isize,isize) = (4,2);
-   | ---------------------- constant defined here
-LL | fn main() {
-LL |     match 42 { A => () }
-   |           --   ^
-   |           |    |
-   |           |    expected integer, found `(isize, isize)`
-   |           |    `A` is interpreted as a constant, not a new binding
-   |           |    help: introduce a new binding instead: `other_a`
-   |           this expression has type `{integer}`
-   |
-   = note: expected type `{integer}`
-             found tuple `(isize, isize)`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/issues/issue-17758.rs b/tests/ui/lifetimes/trait-method-lifetime-suggestion.rs
similarity index 50%
rename from tests/ui/issues/issue-17758.rs
rename to tests/ui/lifetimes/trait-method-lifetime-suggestion.rs
index e2ee84694e390..39cf4ae641857 100644
--- a/tests/ui/issues/issue-17758.rs
+++ b/tests/ui/lifetimes/trait-method-lifetime-suggestion.rs
@@ -1,5 +1,6 @@
-// Test that regionck suggestions in a provided method of a trait
-// don't ICE
+//! regression test for https://github.com/rust-lang/rust/issues/17758
+//! Test that regionck suggestions in a provided method of a trait
+//! don't ICE
 
 trait Foo<'a> {
     fn foo(&'a self);
diff --git a/tests/ui/issues/issue-17758.stderr b/tests/ui/lifetimes/trait-method-lifetime-suggestion.stderr
similarity index 87%
rename from tests/ui/issues/issue-17758.stderr
rename to tests/ui/lifetimes/trait-method-lifetime-suggestion.stderr
index 7a7d2374ef879..64347577d0704 100644
--- a/tests/ui/issues/issue-17758.stderr
+++ b/tests/ui/lifetimes/trait-method-lifetime-suggestion.stderr
@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/issue-17758.rs:7:9
+  --> $DIR/trait-method-lifetime-suggestion.rs:8:9
    |
 LL | trait Foo<'a> {
    |           -- lifetime `'a` defined here
diff --git a/tests/ui/lint/lint-missing-doc-crate-attr.rs b/tests/ui/lint/lint-missing-doc-crate-attr.rs
new file mode 100644
index 0000000000000..51959785c53bd
--- /dev/null
+++ b/tests/ui/lint/lint-missing-doc-crate-attr.rs
@@ -0,0 +1,4 @@
+// regression test for https://github.com/rust-lang/rust/issues/10656
+#![deny(missing_docs)]
+//~^ ERROR missing documentation for the crate
+#![crate_type = "lib"]
diff --git a/tests/ui/issues/issue-10656.stderr b/tests/ui/lint/lint-missing-doc-crate-attr.stderr
similarity index 58%
rename from tests/ui/issues/issue-10656.stderr
rename to tests/ui/lint/lint-missing-doc-crate-attr.stderr
index 61828f9c02a6c..caff87df664b3 100644
--- a/tests/ui/issues/issue-10656.stderr
+++ b/tests/ui/lint/lint-missing-doc-crate-attr.stderr
@@ -1,12 +1,13 @@
 error: missing documentation for the crate
-  --> $DIR/issue-10656.rs:1:1
+  --> $DIR/lint-missing-doc-crate-attr.rs:2:1
    |
 LL | / #![deny(missing_docs)]
-LL | | #![crate_type="lib"]
-   | |____________________^
+LL | |
+LL | | #![crate_type = "lib"]
+   | |______________________^
    |
 note: the lint level is defined here
-  --> $DIR/issue-10656.rs:1:9
+  --> $DIR/lint-missing-doc-crate-attr.rs:2:9
    |
 LL | #![deny(missing_docs)]
    |         ^^^^^^^^^^^^
diff --git a/tests/ui/lint/lint-missing-doc-crate.rs b/tests/ui/lint/lint-missing-doc-crate-flags.rs
similarity index 100%
rename from tests/ui/lint/lint-missing-doc-crate.rs
rename to tests/ui/lint/lint-missing-doc-crate-flags.rs
diff --git a/tests/ui/lint/lint-missing-doc-crate.stderr b/tests/ui/lint/lint-missing-doc-crate-flags.stderr
similarity index 81%
rename from tests/ui/lint/lint-missing-doc-crate.stderr
rename to tests/ui/lint/lint-missing-doc-crate-flags.stderr
index 8efd3a17263fe..040d60a56ebf0 100644
--- a/tests/ui/lint/lint-missing-doc-crate.stderr
+++ b/tests/ui/lint/lint-missing-doc-crate-flags.stderr
@@ -1,5 +1,5 @@
 error: missing documentation for the crate
-  --> $DIR/lint-missing-doc-crate.rs:4:47
+  --> $DIR/lint-missing-doc-crate-flags.rs:4:47
    |
 LL |
    |                                              ^
diff --git a/tests/ui/issues/issue-19734.rs b/tests/ui/macros/undefined-macro-in-impl.rs
similarity index 60%
rename from tests/ui/issues/issue-19734.rs
rename to tests/ui/macros/undefined-macro-in-impl.rs
index fe4a327aef49c..64b394f984be0 100644
--- a/tests/ui/issues/issue-19734.rs
+++ b/tests/ui/macros/undefined-macro-in-impl.rs
@@ -1,3 +1,4 @@
+//! regression test for https://github.com/rust-lang/rust/issues/19734
 fn main() {}
 
 struct Type;
diff --git a/tests/ui/issues/issue-19734.stderr b/tests/ui/macros/undefined-macro-in-impl.stderr
similarity index 75%
rename from tests/ui/issues/issue-19734.stderr
rename to tests/ui/macros/undefined-macro-in-impl.stderr
index ed48714fe5078..8d1bd958d7f6a 100644
--- a/tests/ui/issues/issue-19734.stderr
+++ b/tests/ui/macros/undefined-macro-in-impl.stderr
@@ -1,5 +1,5 @@
 error: cannot find macro `undef` in this scope
-  --> $DIR/issue-19734.rs:6:5
+  --> $DIR/undefined-macro-in-impl.rs:7:5
    |
 LL |     undef!();
    |     ^^^^^
diff --git a/tests/ui/match/match-const-tuple-type-mismatch.rs b/tests/ui/match/match-const-tuple-type-mismatch.rs
new file mode 100644
index 0000000000000..c9358e3d5faac
--- /dev/null
+++ b/tests/ui/match/match-const-tuple-type-mismatch.rs
@@ -0,0 +1,13 @@
+//! Regression test for issue https://github.com/rust-lang/rust/issues/4968
+//@ dont-require-annotations: NOTE
+
+const A: (isize, isize) = (4, 2);
+fn main() {
+    match 42 {
+        A => (),
+        //~^ ERROR mismatched types
+        //~| NOTE expected type `{integer}`
+        //~| NOTE found tuple `(isize, isize)`
+        //~| NOTE expected integer, found `(isize, isize)`
+    }
+}
diff --git a/tests/ui/match/match-const-tuple-type-mismatch.stderr b/tests/ui/match/match-const-tuple-type-mismatch.stderr
new file mode 100644
index 0000000000000..e7dd97c4e9a60
--- /dev/null
+++ b/tests/ui/match/match-const-tuple-type-mismatch.stderr
@@ -0,0 +1,21 @@
+error[E0308]: mismatched types
+  --> $DIR/match-const-tuple-type-mismatch.rs:7:9
+   |
+LL | const A: (isize, isize) = (4, 2);
+   | ----------------------- constant defined here
+LL | fn main() {
+LL |     match 42 {
+   |           -- this expression has type `{integer}`
+LL |         A => (),
+   |         ^
+   |         |
+   |         expected integer, found `(isize, isize)`
+   |         `A` is interpreted as a constant, not a new binding
+   |         help: introduce a new binding instead: `other_a`
+   |
+   = note: expected type `{integer}`
+             found tuple `(isize, isize)`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/issues/issue-18464.rs b/tests/ui/match/match-range-char-const.rs
similarity index 65%
rename from tests/ui/issues/issue-18464.rs
rename to tests/ui/match/match-range-char-const.rs
index 9950647198395..84881fd56cc0f 100644
--- a/tests/ui/issues/issue-18464.rs
+++ b/tests/ui/match/match-range-char-const.rs
@@ -1,3 +1,4 @@
+//! Regression test for https://github.com/rust-lang/rust/issues/18464
 //@ run-pass
 #![deny(dead_code)]
 
@@ -7,6 +8,6 @@ const HIGH_RANGE: char = '9';
 fn main() {
     match '5' {
         LOW_RANGE..=HIGH_RANGE => (),
-        _ => ()
+        _ => (),
     };
 }
diff --git a/tests/ui/issues/issue-17933.rs b/tests/ui/match/match-static-pattern.rs
similarity index 56%
rename from tests/ui/issues/issue-17933.rs
rename to tests/ui/match/match-static-pattern.rs
index 6da4e6e15284b..5d367f9ec17c7 100644
--- a/tests/ui/issues/issue-17933.rs
+++ b/tests/ui/match/match-static-pattern.rs
@@ -1,9 +1,10 @@
+//! regression test for issue https://github.com/rust-lang/rust/issues/17933
 pub static X: usize = 1;
 
 fn main() {
     match 1 {
-        self::X => { },
+        self::X => {}
         //~^ ERROR expected unit struct, unit variant or constant, found static `self::X`
-        _       => { },
+        _ => {}
     }
 }
diff --git a/tests/ui/issues/issue-17933.stderr b/tests/ui/match/match-static-pattern.stderr
similarity index 80%
rename from tests/ui/issues/issue-17933.stderr
rename to tests/ui/match/match-static-pattern.stderr
index 42a7e04420735..1b111fbcc2dec 100644
--- a/tests/ui/issues/issue-17933.stderr
+++ b/tests/ui/match/match-static-pattern.stderr
@@ -1,7 +1,7 @@
 error[E0532]: expected unit struct, unit variant or constant, found static `self::X`
-  --> $DIR/issue-17933.rs:5:9
+  --> $DIR/match-static-pattern.rs:6:9
    |
-LL |         self::X => { },
+LL |         self::X => {}
    |         ^^^^^^^ not a unit struct, unit variant or constant
 
 error: aborting due to 1 previous error
diff --git a/tests/ui/issues/issue-16783.rs b/tests/ui/moves/array-copy-move.rs
similarity index 56%
rename from tests/ui/issues/issue-16783.rs
rename to tests/ui/moves/array-copy-move.rs
index 2ecc42b579d50..ea95bc06a3693 100644
--- a/tests/ui/issues/issue-16783.rs
+++ b/tests/ui/moves/array-copy-move.rs
@@ -1,3 +1,4 @@
+//! regression test for issue https://github.com/rust-lang/rust/issues/16783
 //@ run-pass
 #![allow(unused_variables)]
 
diff --git a/tests/ui/issues/issue-17373.rs b/tests/ui/never_type/never-deref.rs
similarity index 51%
rename from tests/ui/issues/issue-17373.rs
rename to tests/ui/never_type/never-deref.rs
index dc3be48a7ead7..6e4b89db04a54 100644
--- a/tests/ui/issues/issue-17373.rs
+++ b/tests/ui/never_type/never-deref.rs
@@ -1,3 +1,4 @@
+//! regression test for https://github.com/rust-lang/rust/issues/17373
 fn main() {
     *return //~ ERROR type `!` cannot be dereferenced
     ;
diff --git a/tests/ui/issues/issue-17373.stderr b/tests/ui/never_type/never-deref.stderr
similarity index 87%
rename from tests/ui/issues/issue-17373.stderr
rename to tests/ui/never_type/never-deref.stderr
index 0e16d08c87d34..76f31f3779878 100644
--- a/tests/ui/issues/issue-17373.stderr
+++ b/tests/ui/never_type/never-deref.stderr
@@ -1,5 +1,5 @@
 error[E0614]: type `!` cannot be dereferenced
-  --> $DIR/issue-17373.rs:2:5
+  --> $DIR/never-deref.rs:3:5
    |
 LL |     *return
    |     ^^^^^^^ can't be dereferenced
diff --git a/tests/ui/issues/issue-22644.rs b/tests/ui/parser/cast-angle-bracket-precedence.rs
similarity index 92%
rename from tests/ui/issues/issue-22644.rs
rename to tests/ui/parser/cast-angle-bracket-precedence.rs
index e3ada65049d56..65b598d03bdef 100644
--- a/tests/ui/issues/issue-22644.rs
+++ b/tests/ui/parser/cast-angle-bracket-precedence.rs
@@ -1,3 +1,5 @@
+//! regression test for https://github.com/rust-lang/rust/issues/22644
+
 fn main() {
     let a: usize = 0;
     let long_name: usize = 0;
diff --git a/tests/ui/issues/issue-22644.stderr b/tests/ui/parser/cast-angle-bracket-precedence.stderr
similarity index 89%
rename from tests/ui/issues/issue-22644.stderr
rename to tests/ui/parser/cast-angle-bracket-precedence.stderr
index c6d41cc856dd4..975bfea9425aa 100644
--- a/tests/ui/issues/issue-22644.stderr
+++ b/tests/ui/parser/cast-angle-bracket-precedence.stderr
@@ -1,5 +1,5 @@
 error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
-  --> $DIR/issue-22644.rs:6:31
+  --> $DIR/cast-angle-bracket-precedence.rs:8:31
    |
 LL |     println!("{}", a as usize < long_name);
    |                               ^ --------- interpreted as generic arguments
@@ -12,7 +12,7 @@ LL |     println!("{}", (a as usize) < long_name);
    |                    +          +
 
 error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
-  --> $DIR/issue-22644.rs:7:33
+  --> $DIR/cast-angle-bracket-precedence.rs:9:33
    |
 LL |     println!("{}{}", a as usize < long_name, long_name);
    |                                 ^ -------------------- interpreted as generic arguments
@@ -25,7 +25,7 @@ LL |     println!("{}{}", (a as usize) < long_name, long_name);
    |                      +          +
 
 error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
-  --> $DIR/issue-22644.rs:9:31
+  --> $DIR/cast-angle-bracket-precedence.rs:11:31
    |
 LL |     println!("{}", a as usize < 4);
    |                               ^ - interpreted as generic arguments
@@ -38,7 +38,7 @@ LL |     println!("{}", (a as usize) < 4);
    |                    +          +
 
 error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
-  --> $DIR/issue-22644.rs:14:20
+  --> $DIR/cast-angle-bracket-precedence.rs:16:20
    |
 LL |                    <
    |                    ^ not interpreted as comparison
@@ -53,7 +53,7 @@ LL ~                    usize)
    |
 
 error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
-  --> $DIR/issue-22644.rs:23:20
+  --> $DIR/cast-angle-bracket-precedence.rs:25:20
    |
 LL |                    <
    |                    ^ not interpreted as comparison
@@ -70,7 +70,7 @@ LL ~                    usize)
    |
 
 error: `<<` is interpreted as a start of generic arguments for `usize`, not a shift
-  --> $DIR/issue-22644.rs:26:31
+  --> $DIR/cast-angle-bracket-precedence.rs:28:31
    |
 LL |     println!("{}", a as usize << long_name);
    |                               ^^ --------- interpreted as generic arguments
diff --git a/tests/ui/issues/issue-27033.rs b/tests/ui/pattern/match-at-pattern-shadows-name.rs
similarity index 58%
rename from tests/ui/issues/issue-27033.rs
rename to tests/ui/pattern/match-at-pattern-shadows-name.rs
index a23819a20f9aa..3cd2040c9fafa 100644
--- a/tests/ui/issues/issue-27033.rs
+++ b/tests/ui/pattern/match-at-pattern-shadows-name.rs
@@ -1,10 +1,12 @@
+//! regression test for https://github.com/rust-lang/rust/issues/27033
 fn main() {
     match Some(1) {
         None @ _ => {} //~ ERROR match bindings cannot shadow unit variants
     };
     const C: u8 = 1;
     match 1 {
-        C @ 2 => { //~ ERROR match bindings cannot shadow constant
+        C @ 2 => {
+            //~^ ERROR match bindings cannot shadow constant
             println!("{}", C);
         }
         _ => {}
diff --git a/tests/ui/issues/issue-27033.stderr b/tests/ui/pattern/match-at-pattern-shadows-name.stderr
similarity index 86%
rename from tests/ui/issues/issue-27033.stderr
rename to tests/ui/pattern/match-at-pattern-shadows-name.stderr
index 129870f8c4098..6e2fbf546e82d 100644
--- a/tests/ui/issues/issue-27033.stderr
+++ b/tests/ui/pattern/match-at-pattern-shadows-name.stderr
@@ -1,5 +1,5 @@
 error[E0530]: match bindings cannot shadow unit variants
-  --> $DIR/issue-27033.rs:3:9
+  --> $DIR/match-at-pattern-shadows-name.rs:4:9
    |
 LL |         None @ _ => {}
    |         ^^^^ cannot be named the same as a unit variant
@@ -9,7 +9,7 @@ LL |         None @ _ => {}
    = note: the unit variant `None` is defined here
 
 error[E0530]: match bindings cannot shadow constants
-  --> $DIR/issue-27033.rs:7:9
+  --> $DIR/match-at-pattern-shadows-name.rs:8:9
    |
 LL |     const C: u8 = 1;
    |     ---------------- the constant `C` is defined here
diff --git a/tests/ui/resolve/module-used-as-struct-constructor.rs b/tests/ui/resolve/module-used-as-struct-constructor.rs
new file mode 100644
index 0000000000000..bdc7b2bf5841f
--- /dev/null
+++ b/tests/ui/resolve/module-used-as-struct-constructor.rs
@@ -0,0 +1,6 @@
+//! regression test for https://github.com/rust-lang/rust/issues/17001, https://github.com/rust-lang/rust/issues/21449, https://github.com/rust-lang/rust/issues/23189
+mod foo {}
+
+fn main() {
+    let p = foo { x: () }; //~ ERROR expected struct, variant or union type, found module `foo`
+}
diff --git a/tests/ui/issues/issue-17001.stderr b/tests/ui/resolve/module-used-as-struct-constructor.stderr
similarity index 83%
rename from tests/ui/issues/issue-17001.stderr
rename to tests/ui/resolve/module-used-as-struct-constructor.stderr
index 6ea32e0a45c39..b94a28762a7f8 100644
--- a/tests/ui/issues/issue-17001.stderr
+++ b/tests/ui/resolve/module-used-as-struct-constructor.stderr
@@ -1,5 +1,5 @@
 error[E0574]: expected struct, variant or union type, found module `foo`
-  --> $DIR/issue-17001.rs:4:13
+  --> $DIR/module-used-as-struct-constructor.rs:5:13
    |
 LL |     let p = foo { x: () };
    |             ^^^ not a struct, variant or union type
diff --git a/tests/ui/issues/issue-34047.rs b/tests/ui/shadowed/match-binding-shadows-const.rs
similarity index 66%
rename from tests/ui/issues/issue-34047.rs
rename to tests/ui/shadowed/match-binding-shadows-const.rs
index 55196177f6934..95f2e087b5e7f 100644
--- a/tests/ui/issues/issue-34047.rs
+++ b/tests/ui/shadowed/match-binding-shadows-const.rs
@@ -1,3 +1,4 @@
+//! regression test for https://github.com/rust-lang/rust/issues/34047
 const C: u8 = 0;
 
 fn main() {
diff --git a/tests/ui/issues/issue-34047.stderr b/tests/ui/shadowed/match-binding-shadows-const.stderr
similarity index 87%
rename from tests/ui/issues/issue-34047.stderr
rename to tests/ui/shadowed/match-binding-shadows-const.stderr
index 97b1230ce3509..345c67700e626 100644
--- a/tests/ui/issues/issue-34047.stderr
+++ b/tests/ui/shadowed/match-binding-shadows-const.stderr
@@ -1,5 +1,5 @@
 error[E0530]: match bindings cannot shadow constants
-  --> $DIR/issue-34047.rs:5:13
+  --> $DIR/match-binding-shadows-const.rs:6:13
    |
 LL | const C: u8 = 0;
    | ---------------- the constant `C` is defined here
diff --git a/tests/ui/statics/static-mut-unsafe-init.rs b/tests/ui/statics/static-mut-unsafe-init.rs
new file mode 100644
index 0000000000000..ee8472100a08e
--- /dev/null
+++ b/tests/ui/statics/static-mut-unsafe-init.rs
@@ -0,0 +1,8 @@
+//! regression test for https://github.com/rust-lang/rust/issues/17450
+//@ build-pass
+#![allow(dead_code)]
+
+static mut X: isize = 3;
+static mut Y: isize = unsafe { X };
+
+fn main() {}
diff --git a/tests/ui/threads-sendsync/thread-join-unwrap.rs b/tests/ui/threads-sendsync/thread-join-unwrap.rs
new file mode 100644
index 0000000000000..6288e15b18741
--- /dev/null
+++ b/tests/ui/threads-sendsync/thread-join-unwrap.rs
@@ -0,0 +1,9 @@
+//! Regression test for unwrapping the result of `join`, issue https://github.com/rust-lang/rust/issues/21291
+//@ run-pass
+//@ needs-threads
+
+use std::thread;
+
+fn main() {
+    thread::spawn(|| {}).join().unwrap()
+}
diff --git a/tests/ui/issues/issue-20162.rs b/tests/ui/trait-bounds/sort-missing-ord-bound.rs
similarity index 50%
rename from tests/ui/issues/issue-20162.rs
rename to tests/ui/trait-bounds/sort-missing-ord-bound.rs
index b491bc37f5153..8d4ea88150175 100644
--- a/tests/ui/issues/issue-20162.rs
+++ b/tests/ui/trait-bounds/sort-missing-ord-bound.rs
@@ -1,4 +1,7 @@
-struct X { x: i32 }
+//! regression test for issue https://github.com/rust-lang/rust/issues/20162
+struct X {
+    x: i32,
+}
 
 fn main() {
     let mut b: Vec<X> = vec![];
diff --git a/tests/ui/issues/issue-20162.stderr b/tests/ui/trait-bounds/sort-missing-ord-bound.stderr
similarity index 88%
rename from tests/ui/issues/issue-20162.stderr
rename to tests/ui/trait-bounds/sort-missing-ord-bound.stderr
index 8f45f0d36c71e..c11781e5fff3f 100644
--- a/tests/ui/issues/issue-20162.stderr
+++ b/tests/ui/trait-bounds/sort-missing-ord-bound.stderr
@@ -1,5 +1,5 @@
 error[E0277]: the trait bound `X: Ord` is not satisfied
-  --> $DIR/issue-20162.rs:5:7
+  --> $DIR/sort-missing-ord-bound.rs:8:7
    |
 LL |     b.sort();
    |       ^^^^ the trait `Ord` is not implemented for `X`
@@ -9,7 +9,7 @@ note: required by a bound in `slice::<impl [T]>::sort`
 help: consider annotating `X` with `#[derive(Ord)]`
    |
 LL + #[derive(Ord)]
-LL | struct X { x: i32 }
+LL | struct X {
    |
 
 error: aborting due to 1 previous error
diff --git a/tests/ui/traits/solver-cycles/assoc-equality-cycle.rs b/tests/ui/traits/solver-cycles/assoc-equality-cycle.rs
new file mode 100644
index 0000000000000..f82bffc598b8b
--- /dev/null
+++ b/tests/ui/traits/solver-cycles/assoc-equality-cycle.rs
@@ -0,0 +1,10 @@
+//! regression test for https://github.com/rust-lang/rust/issues/21177
+trait Trait {
+    type A;
+    type B;
+}
+
+fn foo<T: Trait<A = T::B>>() {}
+//~^ ERROR cycle detected
+
+fn main() {}
diff --git a/tests/ui/issues/issue-21177.stderr b/tests/ui/traits/solver-cycles/assoc-equality-cycle.stderr
similarity index 78%
rename from tests/ui/issues/issue-21177.stderr
rename to tests/ui/traits/solver-cycles/assoc-equality-cycle.stderr
index 9f66f43a195a1..a8c0228601a26 100644
--- a/tests/ui/issues/issue-21177.stderr
+++ b/tests/ui/traits/solver-cycles/assoc-equality-cycle.stderr
@@ -1,14 +1,14 @@
 error[E0391]: cycle detected when computing the bounds for type parameter `T`
-  --> $DIR/issue-21177.rs:6:21
+  --> $DIR/assoc-equality-cycle.rs:7:21
    |
-LL | fn foo<T: Trait<A = T::B>>() { }
+LL | fn foo<T: Trait<A = T::B>>() {}
    |                     ^^^^
    |
    = note: ...which immediately requires computing the bounds for type parameter `T` again
 note: cycle used when computing explicit predicates of `foo`
-  --> $DIR/issue-21177.rs:6:21
+  --> $DIR/assoc-equality-cycle.rs:7:21
    |
-LL | fn foo<T: Trait<A = T::B>>() { }
+LL | fn foo<T: Trait<A = T::B>>() {}
    |                     ^^^^
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
diff --git a/tests/ui/traits/solver-cycles/self-item-cycle.rs b/tests/ui/traits/solver-cycles/self-item-cycle.rs
new file mode 100644
index 0000000000000..b0b5ab4235beb
--- /dev/null
+++ b/tests/ui/traits/solver-cycles/self-item-cycle.rs
@@ -0,0 +1,6 @@
+//! regression test for https://github.com/rust-lang/rust/issues/20772
+trait T: Iterator<Item = Self::Item> //~ ERROR cycle detected
+{
+}
+
+fn main() {}
diff --git a/tests/ui/issues/issue-20772.stderr b/tests/ui/traits/solver-cycles/self-item-cycle.stderr
similarity index 69%
rename from tests/ui/issues/issue-20772.stderr
rename to tests/ui/traits/solver-cycles/self-item-cycle.stderr
index 81f80aef59446..9ffb9955af8a5 100644
--- a/tests/ui/issues/issue-20772.stderr
+++ b/tests/ui/traits/solver-cycles/self-item-cycle.stderr
@@ -1,15 +1,15 @@
 error[E0391]: cycle detected when computing the super traits of `T` with associated type name `Item`
-  --> $DIR/issue-20772.rs:1:1
+  --> $DIR/self-item-cycle.rs:2:1
    |
-LL | trait T : Iterator<Item=Self::Item>
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | trait T: Iterator<Item = Self::Item>
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: ...which immediately requires computing the super traits of `T` with associated type name `Item` again
 note: cycle used when computing the super predicates of `T`
-  --> $DIR/issue-20772.rs:1:1
+  --> $DIR/self-item-cycle.rs:2:1
    |
-LL | trait T : Iterator<Item=Self::Item>
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | trait T: Iterator<Item = Self::Item>
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
 error: aborting due to 1 previous error
diff --git a/tests/ui/typeck/missing-type-annotation.rs b/tests/ui/typeck/missing-type-annotation.rs
new file mode 100644
index 0000000000000..d13a7a8559e30
--- /dev/null
+++ b/tests/ui/typeck/missing-type-annotation.rs
@@ -0,0 +1,4 @@
+//! Regression test for https://github.com/rust-lang/rust/issues/18159
+fn main() {
+    let x; //~ ERROR type annotations needed
+}
diff --git a/tests/ui/issues/issue-18159.stderr b/tests/ui/typeck/missing-type-annotation.stderr
similarity index 87%
rename from tests/ui/issues/issue-18159.stderr
rename to tests/ui/typeck/missing-type-annotation.stderr
index 5de13a5c314c5..88716e757a939 100644
--- a/tests/ui/issues/issue-18159.stderr
+++ b/tests/ui/typeck/missing-type-annotation.stderr
@@ -1,5 +1,5 @@
 error[E0282]: type annotations needed
-  --> $DIR/issue-18159.rs:2:9
+  --> $DIR/missing-type-annotation.rs:3:9
    |
 LL |     let x;
    |         ^
diff --git a/tests/ui/issues/issue-49854.rs b/tests/ui/typeck/osstring-str-equality.rs
similarity index 71%
rename from tests/ui/issues/issue-49854.rs
rename to tests/ui/typeck/osstring-str-equality.rs
index b5a3f07dd4b85..47d3dd632bdc1 100644
--- a/tests/ui/issues/issue-49854.rs
+++ b/tests/ui/typeck/osstring-str-equality.rs
@@ -1,3 +1,4 @@
+//! regression test for https://github.com/rust-lang/rust/issues/49854
 //@ run-pass
 use std::ffi::OsString;
 
diff --git a/tests/ui/typeck/return-expression-invalid-callee.rs b/tests/ui/typeck/return-expression-invalid-callee.rs
new file mode 100644
index 0000000000000..1416f3e9ddfe7
--- /dev/null
+++ b/tests/ui/typeck/return-expression-invalid-callee.rs
@@ -0,0 +1,8 @@
+//! regression test for issue https://github.com/rust-lang/rust/issues/18532
+//! Test that overloaded call parameter checking does not ICE
+//! when a type error or unconstrained type variable propagates
+//! into it.
+
+fn main() {
+    (return)((), ()); //~ ERROR expected function, found `!`
+}
diff --git a/tests/ui/issues/issue-18532.stderr b/tests/ui/typeck/return-expression-invalid-callee.stderr
similarity index 67%
rename from tests/ui/issues/issue-18532.stderr
rename to tests/ui/typeck/return-expression-invalid-callee.stderr
index 059c7f137819e..5a36602af8bb6 100644
--- a/tests/ui/issues/issue-18532.stderr
+++ b/tests/ui/typeck/return-expression-invalid-callee.stderr
@@ -1,8 +1,8 @@
 error[E0618]: expected function, found `!`
-  --> $DIR/issue-18532.rs:6:5
+  --> $DIR/return-expression-invalid-callee.rs:7:5
    |
-LL |     (return)((),());
-   |     ^^^^^^^^-------
+LL |     (return)((), ());
+   |     ^^^^^^^^--------
    |     |
    |     call expression requires function