================
@@ -2667,6 +2667,33 @@ void Sema::MergeTypedefNameDecl(Scope *S,
TypedefNameDecl *New,
else
New->setTypeSourceInfo(OldTD->getTypeSourceInfo());
+ // See https://github.com/llvm/llvm-project/issues/213299 for the case.
+ //
+ // Ideally, we shall merge the new enum with the old enum when we
+ // creating the new enum. But the enum is anonymous and the typedef's
name
+ // come after the enum body, it is too late to merge them. This is the
+ // choice 10 years ago: a523022b5384d7a0901beea7a5f36ee9c09ba339.
Actually
+ // what we're merging here is the typedef decls.
+ //
+ // Then https://github.com/llvm/llvm-project/pull/114240 removes the
logic
+ // to remove the new ED. This the direct trigger for the above issue of
+ // ambiguous look ups.
+ //
+ // We choose to fix the problem by setting the type of new enum to the
+ // type of old enums. This is consistent with the above call to
+ // setTypeSourceInfo.
+ //
+ // FIXME: The check `M && M->isGlobalModule()` is not necessary but we
+ // hope to limit the impact of this change. We can relax the check when
we
+ // find similar issue later in other cases.
----------------
vgvassilev wrote:
```suggestion
// An anonymous enum is recognized as a redeclaration only when its
typedef
// name gets merged, at which point two distinct enum types already exist.
// Retype the new enumerators to the old enum type, matching the typedef
// merge above; otherwise the merged typedef and its enumerators disagree
// on the type (GH213299).
//
// FIXME: The global module restriction only limits the impact of this
// change; relax it if the issue shows up in other contexts.
```
https://github.com/llvm/llvm-project/pull/214121
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