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

[Emily Dror via cfe-commits]

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@@ -8229,24 +8229,37 @@ Sema::CheckTemplateDeclScope(Scope *S, TemplateParameterList *TemplateParams) {
   // C++ [temp.class.spec]p6: [P2096]
   //   A partial specialization may be declared in any scope in which the
   //   corresponding primary template may be defined.
+  auto FindTemplateParamsLoc = [](TemplateParameterList *TemplateParams,
+                                  SourceLocation Fallback) {
+    SourceLocation DiagLoc = TemplateParams->getTemplateLoc();
+    if (DiagLoc.isValid())
+      return DiagLoc;
+
+    for (const NamedDecl *Param : *TemplateParams)
+      if (Param && Param->getLocation().isValid())
+        return Param->getLocation();
+
+    return Fallback;
+  };
+
   if (Ctx) {
     if (Ctx->isFileContext())
       return false;
     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(),
+      if (RD->isLocalClass()) {
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emily-dror wrote:

Oops, thanks for pointing that out. I'll change it :)

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