Fun with double arrow / hash rocket in Swift

gistfile1.swift

operator infix => { associativity left }
func => <K : Hashable, V>(key: K, value: V) -> (K, V) {
    return (key, value)
}

let pairs: (String, Int)[] = [
    "e" => 10,
    "t" => 7,
    "i" => 2
]

This is cool. Do you need associativity? "a" => "b" => "c" doesn't make sense anyway since tuples aren't Hashable.

Swift seems to have no problem with it if you leave out associativity but every mention of custom infix operators in the docs declares associativity out of convention.