improve comment wording before diagnostics

Author: vbvictor

clang/lib/Sema/SemaExprCXX.cpp

@@ -2753,7 +2753,7 @@ static bool resolveAllocationOverloadInterior(
     if (Diagnose) {
       // If this is an allocation of the form 'new (p) X' for some object
       // pointer p (or an expression that will decay to such a pointer),
-      // diagnose potential error.
+      // diagnose the reason for the error.
       if (!R.isClassLookup() && Args.size() == 2 &&
           (Args[1]->getType()->isObjectPointerType() ||
            Args[1]->getType()->isArrayType())) {