Clarify behavior of access note with ObjCName only

An access note with an ObjCName property but no ObjC property now implicitly sets ObjC to true. ObjC: false with an ObjCName is still illegal.

Author: beccadax

lib/AST/AccessNotes.cpp

@@ -255,8 +255,12 @@ void MappingTraits<AccessNote>::mapping(IO &io, AccessNote &note) {
 }
 
 StringRef MappingTraits<AccessNote>::validate(IO &io, AccessNote &note) {
-  if (!note.ObjC.getValueOr(true) && note.ObjCName.hasValue())
+  if (note.ObjCName.hasValue()) {
+    if (!note.ObjC)
+      note.ObjC = true;
+    else if (!*note.ObjC)
     return "cannot have an 'ObjCName' if 'ObjC' is false";
+  }
 
   return "";
 }

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1500,7 +1500,7 @@ static void applyAccessNote(ValueDecl *VD, const AccessNote &note,
   ASTContext &ctx = VD->getASTContext();
 
   addOrRemoveAttr<ObjCAttr>(VD, notes, note.ObjC, [&]() {
-    return ObjCAttr::create(ctx, note.ObjCName, true);
+    return ObjCAttr::create(ctx, note.ObjCName, false);
   });
 
   addOrRemoveAttr<DynamicAttr>(VD, notes, note.Dynamic, [&]{
@@ -1509,11 +1509,9 @@ static void applyAccessNote(ValueDecl *VD, const AccessNote &note,
 
   if (note.ObjCName) {
     auto attr = VD->getAttrs().getAttribute<ObjCAttr>();
+    assert(attr && "ObjCName set, but ObjCAttr not true or did not apply???");
 
-    if (!attr) {
-      // TODO: diagnose use of ObjCName without ObjC: true
-    }
-    else if (!attr->hasName()) {
+    if (!attr->hasName()) {
       attr->setName(*note.ObjCName, true);
       ctx.Diags.diagnose(attr->getLocation(),
                          diag::attr_objc_name_changed_by_access_note,

test/SILGen/objc_access_notes.swift

@@ -107,7 +107,7 @@ class Hoozit : Gizmo {
 
   // NS_RETURNS_RETAINED by family (-copy)
   // expected-warning@+2 {{access note for fancy test suite adds attribute 'objc' to this instance method}}
-  // expected-note@+1 {{add attribute explicitly to silence this warning}} {{3-3=@objc }}
+  // expected-note@+1 {{add attribute explicitly to silence this warning}} {{3-3=@objc(copyDuplicate) }}
   func makeDuplicate() -> Gizmo { return self }
   // CHECK-LABEL: sil hidden [thunk] [ossa] @$s11objc_thunks6HoozitC13makeDuplicateSo5GizmoCyFTo : $@convention(objc_method) (Hoozit) -> @owned Gizmo
   // CHECK: bb0([[THIS:%.*]] : @unowned $Hoozit):