[clang] [Clang] Fix assertion failure when passing wide string literal to __builtin_nanf (PR #205452)

[Aaron Ballman via cfe-commits]

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@@ -19999,6 +19999,8 @@ static bool TryEvaluateBuiltinNaN(const ASTContext &Context,
   const StringLiteral *S = dyn_cast<StringLiteral>(Arg->IgnoreParenCasts());
   if (!S) return false;
 
+  if (!S->isOrdinary() && !S->isUTF8()) return false;
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AaronBallman wrote:

I think we only want ordinary string literals; I don't think we want to support `u8"whatever"` unless there are compelling use cases.

https://github.com/llvm/llvm-project/pull/205452