[clang] [clang] Fix ASTWriter crash after merging named enums (PR #114240)

[Michael Jabbour via cfe-commits]

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@@ -2551,18 +2551,7 @@ void Sema::MergeTypedefNameDecl(Scope *S, TypedefNameDecl *New,
       // Make the old tag definition visible.
       makeMergedDefinitionVisible(Hidden);
 
-      // If this was an unscoped enumeration, yank all of its enumerators
-      // out of the scope.
-      if (isa<EnumDecl>(NewTag)) {
-        Scope *EnumScope = getNonFieldDeclScope(S);
-        for (auto *D : NewTag->decls()) {
-          auto *ED = cast<EnumConstantDecl>(D);
-          assert(EnumScope->isDeclScope(ED));
-          EnumScope->RemoveDecl(ED);
-          IdResolver.RemoveDecl(ED);
-          ED->getLexicalDeclContext()->removeDecl(ED);
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michael-jabbour-sonarsource wrote:

Thank you all for looking into this :pray:

> Can we solve this issue by reusing some level of modules-specific declaration shadowing?

I am new to modules, and I only learned how this part of the code works while debugging the crash I am sharing here. I am not entirely sure I understand what this means, could you provide some pointers that I can start from (e.g. function names, commits, ...etc)?

I can try to dig into this at the end of this week or next week if needed...

https://github.com/llvm/llvm-project/pull/114240