[clang] [C23] Implement N3018: The constexpr specifier for object definitions (PR #73099)

[Aaron Ballman via cfe-commits]

================
@@ -8857,7 +8894,9 @@ void Sema::CheckVariableDeclarationType(VarDecl *NewVD) {
 
   if (NewVD->isConstexpr() && !T->isDependentType() &&
       RequireLiteralType(NewVD->getLocation(), T,
-                         diag::err_constexpr_var_non_literal)) {
+                         getLangOpts().C23
+                             ? diag::err_c23_constexpr_invalid_type
+                             : diag::err_constexpr_var_non_literal)) {
----------------
AaronBallman wrote:

Do we need a different diagnostic here from C++? C doesn't have the same notion of "literal type" as C++, but that is the predicate we're checking.

https://github.com/llvm/llvm-project/pull/73099