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.

1 files changed, 10 insertions, 0 deletions

diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index 2e6bdae14a8..f17819474ad 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/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,
+}