> Use hand-written parser > > The old parser was written with winnow which is a parser combinator library. While it’s easy to create a parser with parser combinators, it’s generally slower than a hand-written parser, so the first step is to write the parser by hands. Hand-written parser is not only faster but also allows to do more optimizations in the future.

Maintainer of Winnow here. I wish there were more details on this. I switched `toml` / `toml_edit` to being hand written and got some performance boost but I feel like the other things listed would have dwarfed the gains that I got. I wonder if there were sub optimal patterns they employeed that we could find ways to help better guide people.

For anyone going on about "hand written is always better", I disagree. Parser combinators offer a great way to map things back to grammar definitions which makes them much easier to maintainer. Only in extreme circumstances of features and/or performance does it seem worth going hand-written to me.