[purple_turtle]

What is the point of car that on Mondays changes colour to blue and on each first Friday of the year explodes?

If neither you not anyone else can fix it, without more cost than making a proper one?

[ChrisGreenHeur]

Code review exists.

[bgwalter]

Proper code review takes as long as writing the damn thing in the first place and is infinitely more boring. And you still miss things that would have been obvious while writing.

In this special case, you'd have to reverse engineer the grammar from the parser, calculate first/follow sets and then see if the grammar even is what you intended it to be.