Rollup merge of #143168 - Kivooeo:tf16, r=tgross35

`tests/ui`: A New Order [16/N]

> [!NOTE]
>
> Intermediate commits are intended to help review, but will be squashed prior to merge.

Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of rust-lang/rust#133895.

r? `@tgross35`

(just small one to test new method, also I should squash all this commits except move commit, so we after review will end up having like one move commit and one commit with changes, right?)

13 files changed, 76 insertions, 48 deletions

diff --git a/tests/ui/codegen/maximal-hir-to-mir-coverage-flag.rs b/tests/ui/codegen/maximal-hir-to-mir-coverage-flag.rs
new file mode 100644
index 00000000000..64c31beba28
--- /dev/null
+++ b/tests/ui/codegen/maximal-hir-to-mir-coverage-flag.rs
@@ -0,0 +1,12 @@
+//! Test that -Z maximal-hir-to-mir-coverage flag is accepted.
+//!
+//! Original PR: https://github.com/rust-lang/rust/pull/105286
+
+//@ compile-flags: -Zmaximal-hir-to-mir-coverage
+//@ run-pass
+
+fn main() {
+    let x = 1;
+    let y = x + 1;
+    println!("{y}");
+}
diff --git a/tests/ui/missing_debug_impls.rs b/tests/ui/lint/missing-debug-implementations-lint.rs
index 3abc0706887..8a93f052f9c 100644
--- a/tests/ui/missing_debug_impls.rs
+++ b/tests/ui/lint/missing-debug-implementations-lint.rs
@@ -1,3 +1,7 @@
+//! Test the `missing_debug_implementations` lint that warns about public types without Debug.
+//!
+//! See https://github.com/rust-lang/rust/issues/20855
+
 //@ compile-flags: --crate-type lib
 #![deny(missing_debug_implementations)]
 #![allow(unused)]
@@ -10,7 +14,6 @@ pub enum A {} //~ ERROR type does not implement `Debug`
 pub enum B {}
 
 pub enum C {}
-
 impl fmt::Debug for C {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         Ok(())
@@ -23,15 +26,14 @@ pub struct Foo; //~ ERROR type does not implement `Debug`
 pub struct Bar;
 
 pub struct Baz;
-
 impl fmt::Debug for Baz {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         Ok(())
     }
 }
 
+// Private types should not trigger the lint
 struct PrivateStruct;
-
 enum PrivateEnum {}
 
 #[derive(Debug)]
diff --git a/tests/ui/missing_debug_impls.stderr b/tests/ui/lint/missing-debug-implementations-lint.stderr
index 0538f207b44..288ab981034 100644
--- a/tests/ui/missing_debug_impls.stderr
+++ b/tests/ui/lint/missing-debug-implementations-lint.stderr
@@ -1,17 +1,17 @@
 error: type does not implement `Debug`; consider adding `#[derive(Debug)]` or a manual implementation
-  --> $DIR/missing_debug_impls.rs:7:1
+  --> $DIR/missing-debug-implementations-lint.rs:11:1
    |
 LL | pub enum A {}
    | ^^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/missing_debug_impls.rs:2:9
+  --> $DIR/missing-debug-implementations-lint.rs:6:9
    |
 LL | #![deny(missing_debug_implementations)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: type does not implement `Debug`; consider adding `#[derive(Debug)]` or a manual implementation
-  --> $DIR/missing_debug_impls.rs:20:1
+  --> $DIR/missing-debug-implementations-lint.rs:23:1
    |
 LL | pub struct Foo;
    | ^^^^^^^^^^^^^^^
diff --git a/tests/ui/maximal_mir_to_hir_coverage.rs b/tests/ui/maximal_mir_to_hir_coverage.rs
deleted file mode 100644
index e57c83d007e..00000000000
--- a/tests/ui/maximal_mir_to_hir_coverage.rs
+++ /dev/null
@@ -1,10 +0,0 @@
-//@ compile-flags: -Zmaximal-hir-to-mir-coverage
-//@ run-pass
-
-// Just making sure this flag is accepted and doesn't crash the compiler
-
-fn main() {
-  let x = 1;
-  let y = x + 1;
-  println!("{y}");
-}
diff --git a/tests/ui/maybe-bounds.rs b/tests/ui/maybe-bounds.rs
deleted file mode 100644
index 02ed45c656f..00000000000
--- a/tests/ui/maybe-bounds.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-trait Tr: ?Sized {}
-//~^ ERROR `?Trait` is not permitted in supertraits
-
-type A1 = dyn Tr + (?Sized);
-//~^ ERROR `?Trait` is not permitted in trait object types
-type A2 = dyn for<'a> Tr + (?Sized);
-//~^ ERROR `?Trait` is not permitted in trait object types
-
-fn main() {}
diff --git a/tests/ui/method-output-diff-issue-127263.rs b/tests/ui/method-output-diff-issue-127263.rs
deleted file mode 100644
index 85a903e2453..00000000000
--- a/tests/ui/method-output-diff-issue-127263.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-fn bar() {}
-fn foo(x: i32) -> u32 {
-    0
-}
-fn main() {
-    let b: fn() -> u32 = bar; //~ ERROR mismatched types [E0308]
-    let f: fn(i32) = foo; //~ ERROR mismatched types [E0308]
-}
diff --git a/tests/ui/mismatched_types/fn-pointer-mismatch-diagnostics.rs b/tests/ui/mismatched_types/fn-pointer-mismatch-diagnostics.rs
new file mode 100644
index 00000000000..e28ca3e55b5
--- /dev/null
+++ b/tests/ui/mismatched_types/fn-pointer-mismatch-diagnostics.rs
@@ -0,0 +1,16 @@
+//! This test checks that when there's a type mismatch between a function item and
+//! a function pointer, the error message focuses on the actual type difference
+//! (return types, argument types) rather than the confusing "pointer vs item" distinction.
+//!
+//! See https://github.com/rust-lang/rust/issues/127263
+
+fn bar() {}
+
+fn foo(x: i32) -> u32 {
+    0
+}
+
+fn main() {
+    let b: fn() -> u32 = bar; //~ ERROR mismatched types [E0308]
+    let f: fn(i32) = foo; //~ ERROR mismatched types [E0308]
+}
diff --git a/tests/ui/method-output-diff-issue-127263.stderr b/tests/ui/mismatched_types/fn-pointer-mismatch-diagnostics.stderr
index 35b86114f16..8d63f2ea2d3 100644
--- a/tests/ui/method-output-diff-issue-127263.stderr
+++ b/tests/ui/mismatched_types/fn-pointer-mismatch-diagnostics.stderr
@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/method-output-diff-issue-127263.rs:6:26
+  --> $DIR/fn-pointer-mismatch-diagnostics.rs:14:26
    |
 LL |     let b: fn() -> u32 = bar;
    |            -----------   ^^^ expected fn pointer, found fn item
@@ -10,7 +10,7 @@ LL |     let b: fn() -> u32 = bar;
                  found fn item `fn() -> () {bar}`
 
 error[E0308]: mismatched types
-  --> $DIR/method-output-diff-issue-127263.rs:7:22
+  --> $DIR/fn-pointer-mismatch-diagnostics.rs:15:22
    |
 LL |     let f: fn(i32) = foo;
    |            -------   ^^^ expected fn pointer, found fn item
diff --git a/tests/ui/mod-subitem-as-enum-variant.rs b/tests/ui/mod-subitem-as-enum-variant.rs
deleted file mode 100644
index 959024c46f4..00000000000
--- a/tests/ui/mod-subitem-as-enum-variant.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-mod Mod {
-    pub struct FakeVariant<T>(pub T);
-}
-
-fn main() {
-    Mod::FakeVariant::<i32>(0);
-    Mod::<i32>::FakeVariant(0);
-    //~^ ERROR type arguments are not allowed on module `Mod` [E0109]
-}
diff --git a/tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs b/tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs
new file mode 100644
index 00000000000..04963c98765
--- /dev/null
+++ b/tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs
@@ -0,0 +1,18 @@
+//! Test that ?Trait bounds are forbidden in supertraits and trait object types.
+//!
+//! While `?Sized` and other maybe bounds are allowed in type parameter bounds and where clauses,
+//! they are explicitly forbidden in certain syntactic positions:
+//! - As supertraits in trait definitions
+//! - In trait object type expressions
+//!
+//! See https://github.com/rust-lang/rust/issues/20503
+
+trait Tr: ?Sized {}
+//~^ ERROR `?Trait` is not permitted in supertraits
+
+type A1 = dyn Tr + (?Sized);
+//~^ ERROR `?Trait` is not permitted in trait object types
+type A2 = dyn for<'a> Tr + (?Sized);
+//~^ ERROR `?Trait` is not permitted in trait object types
+
+fn main() {}
diff --git a/tests/ui/maybe-bounds.stderr b/tests/ui/traits/maybe-trait-bounds-forbidden-locations.stderr
index 230d11fd0ae..bd0baa580bd 100644
--- a/tests/ui/maybe-bounds.stderr
+++ b/tests/ui/traits/maybe-trait-bounds-forbidden-locations.stderr
@@ -1,5 +1,5 @@
 error[E0658]: `?Trait` is not permitted in supertraits
-  --> $DIR/maybe-bounds.rs:1:11
+  --> $DIR/maybe-trait-bounds-forbidden-locations.rs:10:11
    |
 LL | trait Tr: ?Sized {}
    |           ^^^^^^
@@ -9,7 +9,7 @@ LL | trait Tr: ?Sized {}
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-bounds.rs:4:20
+  --> $DIR/maybe-trait-bounds-forbidden-locations.rs:13:20
    |
 LL | type A1 = dyn Tr + (?Sized);
    |                    ^^^^^^^^
@@ -18,7 +18,7 @@ LL | type A1 = dyn Tr + (?Sized);
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-bounds.rs:6:28
+  --> $DIR/maybe-trait-bounds-forbidden-locations.rs:15:28
    |
 LL | type A2 = dyn for<'a> Tr + (?Sized);
    |                            ^^^^^^^^
diff --git a/tests/ui/type-alias-enum-variants/module-type-args-error.rs b/tests/ui/type-alias-enum-variants/module-type-args-error.rs
new file mode 100644
index 00000000000..9f7dae4f4f5
--- /dev/null
+++ b/tests/ui/type-alias-enum-variants/module-type-args-error.rs
@@ -0,0 +1,16 @@
+//! Test that type arguments are properly rejected on modules.
+//!
+//! Related PR: https://github.com/rust-lang/rust/pull/56225 (RFC 2338 implementation)
+
+mod Mod {
+    pub struct FakeVariant<T>(pub T);
+}
+
+fn main() {
+    // This should work fine - normal generic struct constructor
+    Mod::FakeVariant::<i32>(0);
+
+    // This should error - type arguments not allowed on modules
+    Mod::<i32>::FakeVariant(0);
+    //~^ ERROR type arguments are not allowed on module `Mod` [E0109]
+}
diff --git a/tests/ui/mod-subitem-as-enum-variant.stderr b/tests/ui/type-alias-enum-variants/module-type-args-error.stderr
index 92d972eba42..4c59d19eaa7 100644
--- a/tests/ui/mod-subitem-as-enum-variant.stderr
+++ b/tests/ui/type-alias-enum-variants/module-type-args-error.stderr
@@ -1,5 +1,5 @@
 error[E0109]: type arguments are not allowed on module `Mod`
-  --> $DIR/mod-subitem-as-enum-variant.rs:7:11
+  --> $DIR/module-type-args-error.rs:14:11
    |
 LL |     Mod::<i32>::FakeVariant(0);
    |     ---   ^^^ type argument not allowed