is duplicated by:

• SR-6126 Unexpected casting result in Array/Optional.

Issue Description:

func sameType<T>(_ x: T, _ y: T) {
    print(x, y, T.self)
}

let x = Int?.none
let y = Int??.none
sameType(x, y)

let a: [Int?] = [x]
let b: [Int??] = [y]
sameType(a, b)

This prints

Optional(nil) nil Optional<Optional<Int>>
[nil] [nil] Array<Optional<Optional<Int>>>

That is, the first call both arguments are getting promoted to Int??, and the none in x is getting wrapped in a some to make the Int??, but in the second case, the [Int?] is getting promoted to an [Int??] differently, possibly by (effectively) {{a.map { $0.map { .some($0) } } }}, instead of {{a.map { .some($0) } }} which matches the behaviour of x.