[clang] Reland: [clang] Track function template instantiation from definition (PR #125266)

[Matheus Izvekov via cfe-commits]

================
@@ -2298,6 +2298,13 @@ class FunctionDecl : public DeclaratorDecl,
     FunctionDeclBits.IsLateTemplateParsed = ILT;
   }
 
+  bool isInstantiatedFromMemberTemplate() const {
+    return FunctionDeclBits.IsInstantiatedFromMemberTemplate;
+  }
+  void setInstantiatedFromMemberTemplate(bool Val = true) {
+    FunctionDeclBits.IsInstantiatedFromMemberTemplate = Val;
+  }
+
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mizvekov wrote:

Yes, from new methods in DeclTemplate.h, which themselves are used from SemaTemplateInstantiateDecl.cpp and from the ASTReader / Writer.

https://github.com/llvm/llvm-project/pull/125266