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

- [ ] Golden tests using more complex grammars.

- [ ] Concerning the unusual `pure :: H.Term pure a -> repr a`,
  it may be acceptable to use `H.Term` only internally.

- [ ] Move the `Symantic.Univariant.*` modules into a separate package, maybe `symantic-base`.

- [ ] Golden tests for TH splices as in `singleton`.
      Note that the custom `Setup.hs` to get `ghcFlags` requires `cabal-install-3.4` which does not compile in Nixpkgs yet.

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

- [ ] Consider introducing registers like in ParsleyHaskell.
      The custom `Setup.hs` requires `cabal-install-3.4`
      which does not compile in Nixpkgs yet.

- [ ] Study if the generated parser can easily and without much costs be made reentrant like `attoparsec`.
      In which case it could maybe replace `attoparsec` in `pipes`.