Fix #[type_const] attribute placement validation

Author: camelid

compiler/rustc_attr_parsing/src/attributes/traits.rs

@@ -66,7 +66,8 @@ pub(crate) struct TypeConstParser;
 impl<S: Stage> NoArgsAttributeParser<S> for TypeConstParser {
     const PATH: &[Symbol] = &[sym::type_const];
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
-    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::AssocConst)]);
+    const ALLOWED_TARGETS: AllowedTargets =
+        AllowedTargets::AllowList(&[Allow(Target::Const), Allow(Target::AssocConst)]);
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::TypeConst;
 }
 

compiler/rustc_passes/src/check_attr.rs

@@ -150,9 +150,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::ProcMacroDerive { .. }) => {
                     self.check_proc_macro(hir_id, target, ProcMacroKind::Derive)
                 }
-                &Attribute::Parsed(AttributeKind::TypeConst(attr_span)) => {
-                    self.check_type_const(hir_id, attr_span, target)
-                }
                 Attribute::Parsed(
                     AttributeKind::Stability {
                         span: attr_span,
@@ -243,6 +240,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::ParenSugar(..)
                     | AttributeKind::AllowIncoherentImpl(..)
                     | AttributeKind::Confusables { .. }
+                    | AttributeKind::TypeConst{..}
                     // `#[doc]` is actually a lot more than just doc comments, so is checked below
                     | AttributeKind::DocComment {..}
                     // handled below this loop and elsewhere
@@ -2102,16 +2100,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    fn check_type_const(&self, _hir_id: HirId, attr_span: Span, target: Target) {
-        if matches!(target, Target::AssocConst | Target::Const) {
-            return;
-        } else {
-            self.dcx()
-                .struct_span_err(attr_span, "`#[type_const]` must only be applied to const items")
-                .emit();
-        }
-    }
-
     fn check_rustc_pub_transparent(&self, attr_span: Span, span: Span, attrs: &[Attribute]) {
         if !find_attr!(attrs, AttributeKind::Repr { reprs, .. } => reprs.iter().any(|(r, _)| r == &ReprAttr::ReprTransparent))
             .unwrap_or(false)