The missing `Sequence.first`

[benrimmington]

@nixberg

Unexpectedly:

(1...).lazy.map { $0 }.first  // (Function)
(1...).lazy.map { $0 }.first! // Infinite loop!

(Which, of course, can be fixed by defining your own Sequence.first.)

This part could also be "fixed" by requiring .first(where:) instead of .first

Require parameter names when referencing to functions

Hi everyone, Some of you may remember SE-0220, my proposal that added the count(where:) function to sequences. This proposal was ultimately accepted in time for Swift 5, but sadly had to be reverted because it was causing issues with the type checker. The issue was that when you reference count, in an expression like myArray.count * 5, you could be referring to the count property, with type Int, or the count(where:) function, which has type ((Element) -> Bool) -> Int, which you can refer to in…