[clang] [clang][Sema] fix crash on __type_pack_element with dependent packs (GH180307) (PR #180407)

[via cfe-commits]

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@@ -3406,25 +3406,39 @@ static QualType checkBuiltinTemplateIdType(
     Sema &SemaRef, ElaboratedTypeKeyword Keyword, BuiltinTemplateDecl *BTD,
     ArrayRef<TemplateArgument> Converted, SourceLocation TemplateLoc,
     TemplateArgumentListInfo &TemplateArgs) {
+  TemplateParameterList *Params = BTD->getTemplateParameters();
+  unsigned RequiredArgs = Params->size();
+  if (Params->hasParameterPack()) {
+    if (Converted.size() < RequiredArgs)
+      return QualType();
+  } else {
+    if (Converted.size() != RequiredArgs)
+      return QualType();
+  }
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Serosh-commits wrote:

> @mizvekov what would be the correct way to do this check? I could write a bunch of code to do it manually of course, but it seems like something that must surely need to be done elsewhere? (though I guess the "elsewhere" would be user defined functions where the code would have an actual TemplateArgumentList or similar it was checking against)

@ojhunt let me try to find something or do u have some ideas for the correct check let me know

https://github.com/llvm/llvm-project/pull/180407