Sema: Accept @_implementationOnly on enums and classes

Author: xymus

include/swift/AST/DeclAttr.def

@@ -474,7 +474,7 @@ SIMPLE_DECL_ATTR(_alwaysEmitIntoClient, AlwaysEmitIntoClient,
   83)
 
 SIMPLE_DECL_ATTR(_implementationOnly, ImplementationOnly,
-  OnImport | OnFunc | OnConstructor | OnVar | OnSubscript | OnStruct,
+  OnImport | OnFunc | OnConstructor | OnVar | OnSubscript | OnStruct | OnClass | OnEnum,
   UserInaccessible | ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove | UnreachableInABIAttr,
   84)
 

include/swift/AST/DiagnosticsSema.def

@@ -3949,8 +3949,8 @@ ERROR(implementation_only_override_import_without_attr,none,
       "override of %kindonly0 imported as implementation-only must be declared "
       "'@_implementationOnly'",
       (const ValueDecl *))
-ERROR(implementation_only_on_structs_feature,none,
-      "'@_implementationOnly' on structs requires "
+ERROR(implementation_only_on_types_feature,none,
+      "'@_implementationOnly' on a type requires "
       "'-enable-experimental-feature CheckImplementationOnly'", ())
 
 ERROR(import_attr_conflict,none,

lib/Sema/TypeCheckAttr.cpp

@@ -4995,12 +4995,12 @@ AttributeChecker::visitImplementationOnlyAttr(ImplementationOnlyAttr *attr) {
     return;
   }
 
-  // @_implementationOnly on structs only applies to non-public types.
   auto *VD = cast<ValueDecl>(D);
-  if (isa<StructDecl>(VD)) {
+
+  // @_implementationOnly on types only applies to non-public types.
+  if (isa<NominalTypeDecl>(D)) {
     if (!Ctx.LangOpts.hasFeature(Feature::CheckImplementationOnly)) {
-      diagnoseAndRemoveAttr(attr,
-          diag::implementation_only_on_structs_feature);
+      diagnoseAndRemoveAttr(attr, diag::implementation_only_on_types_feature);
       return;
     }
 

test/attr/attr_implementation_only_on_types_feature_required.swift

@@ -0,0 +1,4 @@
+// RUN: %target-typecheck-verify-swift %s
+
+@_implementationOnly struct MyStruct {}
+// expected-error@-1{{'@_implementationOnly' on a type requires '-enable-experimental-feature CheckImplementationOnly'}}