[NFC] Fix ImplementsAttr::clone()

Author: beccadax

include/swift/AST/Attr.h

@@ -1725,14 +1725,16 @@ class StorageRestrictionsAttr final
 /// The @_implements attribute, which treats a decl as the implementation for
 /// some named protocol requirement (but otherwise not-visible by that name).
 class ImplementsAttr : public DeclAttribute {
-  TypeRepr *TyR;
+  /// If constructed by the \c create() variant with a TypeRepr, the TypeRepr;
+  /// if constructed by the \c create() variant with a DeclContext and
+  /// ProtocolDecl, the DeclContext.
+  llvm::PointerUnion<TypeRepr *, DeclContext *> TyROrDC;
   DeclName MemberName;
   DeclNameLoc MemberNameLoc;
 
   ImplementsAttr(SourceLoc atLoc, SourceRange Range,
-                 TypeRepr *TyR,
-                 DeclName MemberName,
-                 DeclNameLoc MemberNameLoc);
+                 llvm::PointerUnion<TypeRepr *, DeclContext *> TyROrDC,
+                 DeclName MemberName, DeclNameLoc MemberNameLoc);
 
 public:
   static ImplementsAttr *create(ASTContext &Ctx, SourceLoc atLoc,
@@ -1752,7 +1754,9 @@ class ImplementsAttr : public DeclAttribute {
   /// otherwise `nullopt`. This should only be used for dumping.
   std::optional<ProtocolDecl *> getCachedProtocol(DeclContext *dc) const;
 
-  TypeRepr *getProtocolTypeRepr() const { return TyR; }
+  TypeRepr *getProtocolTypeRepr() const {
+    return TyROrDC.dyn_cast<TypeRepr *>();
+  }
 
   DeclName getMemberName() const { return MemberName; }
   DeclNameLoc getMemberNameLoc() const { return MemberNameLoc; }
@@ -1763,8 +1767,12 @@ class ImplementsAttr : public DeclAttribute {
 
   /// Create a copy of this attribute.
   ImplementsAttr *clone(ASTContext &ctx) const {
-    return new (ctx) ImplementsAttr(
-        AtLoc, Range, TyR, getMemberName(), getMemberNameLoc());
+    if (auto tyR = getProtocolTypeRepr()) {
+      return create(ctx, AtLoc, Range, tyR, getMemberName(),
+                    getMemberNameLoc());
+    }
+    auto dc = TyROrDC.dyn_cast<DeclContext *>();
+    return create(dc, getProtocol(dc), getMemberName());
   }
 };
 

lib/AST/Attr.cpp

@@ -2666,11 +2666,12 @@ StorageRestrictionsAttr::create(
                                            /*implicit=*/false);
 }
 
-ImplementsAttr::ImplementsAttr(SourceLoc atLoc, SourceRange range,
-                               TypeRepr *TyR, DeclName MemberName,
-                               DeclNameLoc MemberNameLoc)
+ImplementsAttr::
+ImplementsAttr(SourceLoc atLoc, SourceRange range,
+               llvm::PointerUnion<TypeRepr *, DeclContext *> TyROrDC,
+               DeclName MemberName, DeclNameLoc MemberNameLoc)
     : DeclAttribute(DeclAttrKind::Implements, atLoc, range, /*Implicit=*/false),
-      TyR(TyR), MemberName(MemberName), MemberNameLoc(MemberNameLoc) {}
+      TyROrDC(TyROrDC), MemberName(MemberName), MemberNameLoc(MemberNameLoc) {}
 
 ImplementsAttr *ImplementsAttr::create(ASTContext &Ctx, SourceLoc atLoc,
                                        SourceRange range,
@@ -2687,9 +2688,8 @@ ImplementsAttr *ImplementsAttr::create(DeclContext *DC,
                                        DeclName MemberName) {
   auto &ctx = DC->getASTContext();
   void *mem = ctx.Allocate(sizeof(ImplementsAttr), alignof(ImplementsAttr));
-  auto *attr = new (mem) ImplementsAttr(
-      SourceLoc(), SourceRange(), nullptr,
-      MemberName, DeclNameLoc());
+  auto *attr = new (mem) ImplementsAttr(SourceLoc(), SourceRange(), DC,
+                                        MemberName, DeclNameLoc());
   ctx.evaluator.cacheOutput(ImplementsAttrProtocolRequest{attr, DC},
                             std::move(Proto));
   return attr;