[clang] Don't wrap immediate invocations in ConstantExprs within constexpr initializers (PR #89565)

[Daniel M. Katz via cfe-commits]

================
@@ -2554,16 +2554,26 @@ Decl *Parser::ParseDeclarationAfterDeclarator(
   return ParseDeclarationAfterDeclaratorAndAttributes(D, TemplateInfo);
 }
 
+static bool isConstexprVariable(const Decl *D) {
+  if (const VarDecl *Var = dyn_cast_or_null<VarDecl>(D))
----------------
katzdm wrote:

@cor3ntin I take it back - I think this can be null during certain error codepaths (I got some crashes in a handful of tests when I changed to `dyn_cast`). Going to use `dyn_cast_if_present` instead.

https://github.com/llvm/llvm-project/pull/89565