add error message when #[naked] is used with #[test]

compiler/rustc_builtin_macros/messages.ftl

@@ -216,6 +216,11 @@ builtin_macros_multiple_defaults = multiple declared defaults
     .note = only one variant can be default
     .suggestion = make `{$ident}` default
 
+builtin_macros_naked_functions_testing_attribute =
+    cannot use `#[naked]` with testing attributes
+    .label = function marked with testing attribute here
+    .naked_attribute = `#[naked]` is incompatible with testing attributes
+
 builtin_macros_no_default_variant = no default declared
     .help = make a unit variant default by placing `#[default]` above it
     .suggestion = make `{$ident}` default

compiler/rustc_builtin_macros/src/errors.rs

@@ -912,3 +912,13 @@ pub(crate) struct ExpectedItem<'a> {
     pub span: Span,
     pub token: &'a str,
 }
+
+#[derive(Diagnostic)]
+#[diag(builtin_macros_naked_functions_testing_attribute, code = E0798)]
+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.