[munificent]

The balancing act is that the fancier your sanity check, the greater the chance of something slipping through its cracks too. Walking too strings in parallel is very simple and hard to get wrong. Traversing an AST and skipping a branch is exactly the kind of easy-to-make bug that the sanity check is designed to catch.

What I'd like to do is something somewhere in the middle where I walk the token stream and check that every token of the input ended up in the output, but I haven't figured out a simple and fast way to do that yet. Performance is particularly tricky because I obviously don't want to burn a bunch of CPU cycles on a sanity check that exists only to catch bugs.