[clang] [RFC][clang] Fix for regression #130917 (PR #132214)

[Matheus Izvekov via cfe-commits]

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@@ -2572,7 +2572,7 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(
   // Friend function defined withing class template may stop being function
   // definition during AST merges from different modules, in this case decl
   // with function body should be used for instantiation.
-  if (isFriend) {
+  if (isFriend && D->hasOwningModule()) {
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mizvekov wrote:

Clang AST is open to modifications.

Can't you add a new bit to `Redeclarable` to keep track of this?

https://github.com/llvm/llvm-project/pull/132214