[clang] [Clang][Modules] Fix crash when redefining default template argument (PR #185237)

[Younan Zhang via cfe-commits]

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@@ -2472,13 +2473,23 @@ bool Sema::CheckTemplateParameterList(TemplateParameterList *NewParams,
         NewDefaultLoc = NewTypeParm->getDefaultArgumentLoc();
         SawDefaultArgument = true;
 
-        if (!OldTypeParm->getOwningModule())
+        bool SameDefault =
+            getASTContext().isSameDefaultTemplateArgument(OldTypeParm,
+                                                          NewTypeParm);
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zyn0217 wrote:

You're repeating the same pattern 3 times. Can you refactor it a bit?

https://github.com/llvm/llvm-project/pull/185237