[clang] [Clang] Don't form a type constraint if the concept is invalid (PR #122065)

[Shafik Yaghmour via cfe-commits]

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@@ -1969,7 +1970,7 @@ void ASTDeclWriter::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
   if (OwnsDefaultArg)
     Record.AddTemplateArgumentLoc(D->getDefaultArgument());
 
-  if (!TC && !OwnsDefaultArg &&
+  if (!D->hasTypeConstraint() && !OwnsDefaultArg &&
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shafik wrote:

The logic here is a little tricky. The new condition is really "it has a constraint and it does not matter if it is initialized".

I feel like this deserves a comment.

It also makes me wonder if "initialized" is the right word here, isn't it really that it was invalid?

I am just thinking of folks coming to maintain this code in the future and understanding the intent and I don't think the intent is 💯 clear as written.

https://github.com/llvm/llvm-project/pull/122065