Fix double error for #[no_mangle] on closures

Author: JonathanBrouwer

compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs

@@ -362,6 +362,7 @@ impl<S: Stage> NoArgsAttributeParser<S> for NoMangleParser {
         Allow(Target::Static),
         Allow(Target::Method(MethodKind::Inherent)),
         Allow(Target::Method(MethodKind::TraitImpl)),
+        Error(Target::Closure),
     ]);
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::NoMangle;
 }

compiler/rustc_codegen_ssa/messages.ftl

@@ -223,8 +223,6 @@ codegen_ssa_multiple_main_functions = entry symbol `main` declared multiple time
 
 codegen_ssa_no_field = no field `{$name}`
 
-codegen_ssa_no_mangle_nameless = `#[no_mangle]` cannot be used on {$definition} as it has no name
-
 codegen_ssa_no_module_named =
     no module named `{$user_path}` (mangled: {$cgu_name}). available modules: {$cgu_names}
 

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -19,7 +19,6 @@ use rustc_span::{Ident, Span, sym};
 use rustc_target::spec::SanitizerSet;
 
 use crate::errors;
-use crate::errors::NoMangleNameless;
 use crate::target_features::{
     check_target_feature_trait_unsafe, check_tied_features, from_target_feature_attr,
 };
@@ -182,14 +181,10 @@ fn process_builtin_attrs(
                     if tcx.opt_item_name(did.to_def_id()).is_some() {
                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
                     } else {
-                        tcx.dcx().emit_err(NoMangleNameless {
-                            span: *attr_span,
-                            definition: format!(
-                                "{} {}",
-                                tcx.def_descr_article(did.to_def_id()),
-                                tcx.def_descr(did.to_def_id())
-                            ),
-                        });
+                        tcx.dcx().span_delayed_bug(
+                            *attr_span,
+                            "no_mangle should be on a named function",
+                        );
                     }
                 }
                 AttributeKind::Optimize(optimize, _) => codegen_fn_attrs.optimize = *optimize,

compiler/rustc_codegen_ssa/src/errors.rs

@@ -1284,14 +1284,6 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_
     }
 }
 
-#[derive(Diagnostic)]
-#[diag(codegen_ssa_no_mangle_nameless)]
-pub(crate) struct NoMangleNameless {
-    #[primary_span]
-    pub span: Span,
-    pub definition: String,
-}
-
 #[derive(Diagnostic)]
 #[diag(codegen_ssa_feature_not_valid)]
 pub(crate) struct FeatureNotValid<'a> {

tests/ui/attributes/no-mangle-closure.rs

@@ -7,5 +7,5 @@ pub struct S([usize; 8]);
 
 pub fn outer_function(x: S, y: S) -> usize {
     (#[no_mangle] || y.0[0])()
-    //~^ ERROR `#[no_mangle]` cannot be used on a closure as it has no name
+    //~^ ERROR `#[no_mangle]` attribute cannot be used on closures
 }

tests/ui/attributes/no-mangle-closure.stderr

@@ -1,8 +1,10 @@
-error: `#[no_mangle]` cannot be used on a closure as it has no name
+error: `#[no_mangle]` attribute cannot be used on closures
   --> $DIR/no-mangle-closure.rs:9:6
    |
 LL |     (#[no_mangle] || y.0[0])()
    |      ^^^^^^^^^^^^
+   |
+   = help: `#[no_mangle]` can be applied to functions, methods, and statics
 
 error: aborting due to 1 previous error