Update infix operator spacing rule to clarify rule for operator definitions like static func ==(lhs: T, rhs: T) -> Bool

[calda]

Summary

This PR proposals an update to the infix operator spacing rule, clarifying that we should omit the trailing space after operators in operator func implementations like static func ==(lhs: T, rhs: T) -> Bool

// WRONG
static func == (_ lhs: MyView, _ rhs: MyView) -> Bool {
  lhs.id == rhs.id
}

// RIGHT
static func ==(_ lhs: MyView, _ rhs: MyView) -> Bool {
  lhs.id == rhs.id
}

Reasoning

The existing wording of the rule implies that it applies in all cases. However, for operator definitions like this, omitting the space is more common.

In our codebase we have 540 examples of func == ( and 709 examples of func ==(. All of the other custom operator definitions I found for other operators (+, -, +=, !=, <, >) also omitted the trailing space.

This is also more consistent with other function definitions. For example, adding a space here looks weird and is disallowed in all other function definitions:

// Looks strange, not allowed
static func isEqual (_ lhs: MyView, _ rhs: MyView) -> Bool {
  lhs.id == rhs.id
}

// Right
static func isEqual(_ lhs: MyView, _ rhs: MyView) -> Bool {
  lhs.id == rhs.id
}

[calda]

This has no effect for now, but will kick in after we enable the spaceAroundOperators rule in a follow-up

[calda]

Removed this example since it was outdated

[calda]

Tweaked this example since consecutive spaces like this are already disallowed by another rule

[calda]

I removed the "Prefer parenthesis" part because it feels separate and doesn't include autocorrect support, and removed the comment on postfix / prefix operators because it's redundant (the rule explicitly only applies to infix operators).

[calda]

Strong support for this change internally 👍🏻