Improve compile time of parser combinators such as Combine

[DemiMarie]

Currently, parser combinator libraries such as Combine require a very long time to type-check. This does not happen with similar Haskell libraries.

This bug can be considered resolved when such libraries do not take too much time to type check.

[bluss]

Please make the issue as specific and actionable as possible. It's best to report specific, measurable issues – they often get fixed!

For example the issue could specify a code snippet that uses combine, the version of the crate, the version of the compiler, and how long it takes to compile.

Previous combine issue: #21231 is fixed since Rust 1.11.

Current PR #36917 will have a positive impact.

[DemiMarie]

Seeing as the underlying issue Marwes/combine#21 was closed, I will close this ticket. Thanks!