[clang] Fix crash with invalid VLA in a type trait (PR #138543)

[Shafik Yaghmour via cfe-commits]

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@@ -41,3 +41,17 @@ void func(int expr) {
   int array[sizeof(Ty) ? sizeof(Ty{}) : sizeof(int)];
   int old_style_assert[expr ? Ty::one : Ty::Neg_one]; // We don't diagnose as a VLA until instantiation
 }
+
+namespace GH138444 {
+struct S {         // expected-note {{candidate constructor (the implicit copy constructor) not viable: no known conversion from 'int' to 'const S &' for 1st argument}} \
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shafik wrote:

I would have liked to see a test for the union case as well since it also triggered the crash. I don't see a way to trigger it w/ the enum case yet. 

https://github.com/llvm/llvm-project/pull/138543