[clang] [C++20][Modules] Fix merging of anonymous members of class templates. (PR #155948)

[Michael Park via cfe-commits]

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@@ -3425,7 +3425,13 @@ NamedDecl *ASTDeclReader::getAnonymousDeclForMerging(ASTReader &Reader,
   // If this is the first time, but we have parsed a declaration of the context,
   // build the anonymous declaration list from the parsed declaration.
   auto *PrimaryDC = getPrimaryDCForAnonymousDecl(DC);
-  if (PrimaryDC && !cast<Decl>(PrimaryDC)->isFromASTFile()) {
+  auto InstantiatedLocally = [](Decl *D, SourceManager &SourceMgr) -> bool {
+    auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(D);
+    return CTSD && CTSD->getPointOfInstantiation().isValid() &&
+           SourceMgr.isLocalSourceLocation(CTSD->getPointOfInstantiation());
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mpark wrote:

Ah... great point. Let me see if I can capture this into a bit flag instead.

https://github.com/llvm/llvm-project/pull/155948