[clang] [clang] fix crash in friend definition (PR #186398)

[Matheus Izvekov via cfe-commits]

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@@ -18461,6 +18408,9 @@ NamedDecl *Sema::ActOnFriendFunctionDecl(Scope *S, Declarator &D,
                                           TemplateParams, AddToScope);
   if (!ND) return nullptr;
 
+  if (WasQualifiedFriendDef)
+    ND->setInvalidDecl();
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mizvekov wrote:

We don't really need to set this, since there is nothing invalid about the declaration now, right?

https://github.com/llvm/llvm-project/pull/186398