[clang] Better diagnostics when assertion fails in `consteval` (PR #130458)

[JJ Marr via cfe-commits]

================
@@ -5975,9 +5975,15 @@ static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
                                         Definition->hasAttr<MSConstexprAttr>())))
     return true;
 
-  if (Info.getLangOpts().CPlusPlus11) {
-    const FunctionDecl *DiagDecl = Definition ? Definition : Declaration;
+  const FunctionDecl *DiagDecl = Definition ? Definition : Declaration;  
+  if (CallLoc.isMacroID() && (DiagDecl->getName() == "__assert_rtn" ||
----------------
jj-marr wrote:

I have no idea how to improve this, otherwise I'd do it. How would I get access to the preprocessor from here?

https://github.com/llvm/llvm-project/pull/130458