Remove separate long function declarations rule

[fdiaz]

Summary

Remove separate long function declarations rule: https://github.com/airbnb/swift/issues/38

Reasoning

Following the new tenet added in this PR #35

Reviewers

cc @airbnb/swift-styleguide-maintainers

[dfed]

Looking forward to the PR where this rule is re-introduced with an autocorrect!

[ljharb]

That tenet uses the word "strive" - that doesn't mean that a non-autocorrectable rule has to be, or even should be, removed from the guide.

[fdiaz]

@ljharb it does for rules that change the format of our code.

If a rule changes the format of the code, it needs to be able to be reformatted automatically (either using SwiftLint autocorrect or SwiftFormat).

This work is part of the "Plan if this is approved" section of this PR #35

[ljharb]

Thanks; if that's what was decided then so be it :-) although there's always going to be things that change the format of the code but aren't safely autofixable, and that's OK.

[fdiaz]

@ljharb yeah, we've decided that those kind of rules will not belong in our style guide. At the end of last year there was a lot of discussion around this issue and on #35 we finally decided on this direction.

That doesn't mean that all rules need to be autocorrected. Only the ones that modify the format of our code. For more details on what this means see this #34 (comment)

Best practices still have a place to be, and even non-lintable rules too as long as they're heavily justified.