Rollup merge of #127853 - folkertdev:naked-function-error-messages, r=bjorn3

`#[naked]`: report incompatible attributes

tracking issue: https://github.com/rust-lang/rust/issues/90957

this is a re-implementation of https://github.com/rust-lang/rust/pull/93809 by ``@bstrie`` which was closed 2 years ago due to inactivity.

This PR takes some of the final comments into account, specifically providing a little more context in error messages, and using an allow list to determine which attributes are compatible with `#[naked]`.

Notable attributes that are incompatible with `#[naked]` are:

  * `#[inline]`
  * `#[track_caller]`
  * ~~`#[target_feature]`~~ (this is now allowed, see PR discussion)
  * `#[test]`, `#[ignore]`, `#[should_panic]`

These attributes just directly conflict with what `#[naked]` should do.

Naked functions are still important for systems programming, embedded, and operating systems, so I'd like to move them forward.

compiler/rustc_builtin_macros/src/errors.rs

@@ -923,3 +923,13 @@ pub(crate) struct ExpectedItem<'a> {
     pub span: Span,
     pub token: &'a str,
 }
+
+#[derive(Diagnostic)]
+#[diag(builtin_macros_naked_functions_testing_attribute, code = E0736)]
+pub struct NakedFunctionTestingAttribute {
+    #[primary_span]
+    #[label(builtin_macros_naked_attribute)]
+    pub naked_span: Span,
+    #[label]
+    pub testing_span: Span,
+}

compiler/rustc_builtin_macros/src/test.rs

@@ -133,6 +133,14 @@ pub(crate) fn expand_test_or_bench(
         };
     };
 
+    if let Some(attr) = attr::find_by_name(&item.attrs, sym::naked) {
+        cx.dcx().emit_err(errors::NakedFunctionTestingAttribute {
+            testing_span: attr_sp,
+            naked_span: attr.span,
+        });
+        return vec![Annotatable::Item(item)];
+    }
+
     // check_*_signature will report any errors in the type so compilation
     // will fail. We shouldn't try to expand in this case because the errors
     // would be spurious.