- [ ] Finalize support for error messages based upon: [A Parsing Machine for Parsing Expression Grammars with Labeled Failures](https://dl.acm.org/doi/10.1145/2851613.2851750)

- [ ] Support parsing tree inputs (eg. RelaxNG in `symantic-xml` or HTTP routing in `symantic-http-server`).

- [ ] Study how the generated parser can be made reentrant like `attoparsec`'s `Partial`.
      In which case it would be able to replace `attoparsec` in `pipes`.

- [ ] Golden tests using more complex grammars.

- [ ] Some static infos should be attached to 'OnException'
      to avoid comparing inputs when they're the same
      and to improve 'checkedHorizon'.