[clang] [clang][Diagnostic] Clarify error message for auto (PR #149781)

[Erich Keane via cfe-commits]

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@@ -8237,12 +8237,24 @@ Sema::CheckTemplateDeclScope(Scope *S, TemplateParameterList *TemplateParams) {
     if (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Ctx)) {
       // C++ [temp.mem]p2:
       //   A local class shall not have member templates.
-      if (RD->isLocalClass())
-        return Diag(TemplateParams->getTemplateLoc(),
-                    diag::err_template_inside_local_class)
-          << TemplateParams->getSourceRange();
-      else
-        return false;
+      if (RD->isLocalClass()) {
+        SourceLocation DiagLoc = TemplateParams->getTemplateLoc();
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erichkeane wrote:

We need to cover 8261 as well.

https://github.com/llvm/llvm-project/pull/149781