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

[Michael Jabbour via cfe-commits]

================
@@ -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);
----------------
michael-jabbour-sonarsource wrote:

Additionally, as far as I can see, for `EnumDeclConstant`s created by the parser, the DeclContext is always the containing `Enum` itself:

https://github.com/llvm/llvm-project/blob/79231a86846b7dff09497fc58ea1e82e892052bd/clang/lib/Sema/SemaDecl.cpp#L19739-L19740

Therefore, after the refactoring I did, I think that the call can be simplified to:

```
ED->removeDecl(ECD);
```


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