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

[Chuanqi Xu via cfe-commits]

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@@ -2472,13 +2473,23 @@ bool Sema::CheckTemplateParameterList(TemplateParameterList *NewParams,
         NewDefaultLoc = NewTypeParm->getDefaultArgumentLoc();
         SawDefaultArgument = true;
 
-        if (!OldTypeParm->getOwningModule())
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ChuanqiXu9 wrote:

if (Module *M = OldTypeParm->getOwningModule(); !M  || !M->isModuleMapModule()) 
    ...

>From your analysis, it seems like we can solve it in this simpler manner?

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