Formatter: make long functions in type annotations easier to read

[jfmengels]

In the following function, I find it hard to read the type for get_visitor, especially that get_visitor is a function.

fn apply_visitor(
  a: a,
  rules: List(rule.ModuleVisitorOperations),
  get_visitor: fn(rule.ModuleVisitorOperations) ->
    option.Option(fn(a) -> rule.ModuleVisitorOperations),
) -> rule.ModuleVisitorOperations {
  todo
}

My suggestion:

fn apply_visitor(
  a: a,
  rules: List(rule.ModuleVisitorOperations),
  get_visitor:
    fn(rule.ModuleVisitorOperations) -> // arrow either here, or on the next line (à la elm-format)
       option.Option(fn(a) -> rule.ModuleVisitorOperations),
) -> rule.ModuleVisitorOperations {
  todo
}

[lpil]

I'm not so sure about this one- I don't find it any easier to read. Could it be this is what you are familiar with rather than it being better?

Would this also apply to let and use and other annotations rather than just functions? Currently we are consistent everywhere with this formatting.

Interested in hearing what others have to say.

[han-tyumi]

I find with the proposed change that the function type is more "together" as you would expect to see it if it were on its own.

I don't think it's a huge difference, but I do find the extra whitespace makes it a bit easier to read the whole function type.