[mrkeen]

> parse with the lalr generated parser, then if that rejects your string because the program was ill formed, call the hand rolled one for guesswork/diagnostics

This feels like a recipe for disaster. If the hand-rolled parser won't match a formal grammar, why would it match the generated parser?

The poor programmer will be debugging the wrong thing.

It reminds me of my short stint writing C++ where I'd read undefined memory in release mode, but when I ran it under debug mode it just worked.

[senkora]

> It reminds me of my short stint writing C++ where I'd read undefined memory in release mode, but when I ran it under debug mode it just worked.

I assume it’s far too late at this point, but that almost always means that you’re invoking UB. Your next step should be enabling UBSan.

[JonChesterfield]

The generated parser will match the grammar.

The hand rolled parser might do, but also might not, what with software being difficult and testing being boring and so forth.

[8n4vidtmkvmk]

There's risk, but it seems like you could run both parsers against the same unit tests to help mitigate.