Adopt some staff from elm parser?

[safareli]

This is interesting alternative to try in ps-parser
https://github.com/elm-tools/parser/blob/2.0.1/src/Parser.elm#L510-L549

Also having problem as sum type is kinda nit
http://package.elm-lang.org/packages/elm-tools/parser/2.0.1/Parser#Problem

[paf31]

I'd rather make a type argument for the error type. We've tried the sum type approach in foreign, and it handles some but not all errors.

Looks like that combinator could be implemented with try fairly easily. We could add something like it.

[jamesdbrock]

Interesting https://github.com/elm/parser/blob/master/README.md

[jamesdbrock]

Hm I think we have a partial solution to this with https://pursuit.purescript.org/packages/purescript-parsing/10.0.0/docs/Parsing.Combinators#v:advance

which was discussed in #120

[jamesdbrock]

It looks like the delayedCommit function has been replaced by backtrackable?

elm/parser#6 (comment)

https://package.elm-lang.org/packages/elm/parser/latest/Parser#backtrackable

Read this document to learn how oneOf, backtrackable, and commit work and interact with each other. It is subtle and important!