Hm. What changed in 4.1? @xedin?

@swift-ci create

(May be a standard library change, we'll see.)

Interesting, since `Optional` is now `Equitable` if '.none', on the right-hand side, is spelled without the base `!=` is inferred as (Foo?, Foo?) -> Bool`, if it's spelled as `Foo.none` it's inferred as `(Foo, Foo) -> Bool`, because `.none` could be interpreted as `Optional.none` instead of `Foo.none`.

/cc @moiseev

/cc @DougGregor

As @xedin notes, `.none` could be interpreted either way. The `Foo.none` solution is better, in the sense that it doesn't require an optional injection on the left-hand side of the `!=` operator, so Swift 4.0 was correct to choose it.

@DougGregor Bigger issue here is that both `!=` overloads that form solutions are declared in protocol extensions, one on `Equatable` `(Self, Self) -> Bool` and another one on `Optional` `(Wrapped?, Wrapped?) -> Bool` and the latter one is more specialized because it's conditional on associated type, that's why we pick `.none` to be `Optional.none` in that example.