struct S<T> { var x: T mutating func exchangeSecond<U>(_ u: U, _ t: T) -> (U, T) { x = t return (u, x) } } extension S where T == Float { mutating func exchangeSecond(_ u: Int, _ t: Float) -> (Int, Float){ x = t return (u, x) } }struct S<T> { var x: T mutating func exchangeSecond<U>(_ u: U, _ t: T) -> (U, T) { x = t return (u, x) } } extension S where T == Float { mutating func exchangeSecond(_ u: Int, _ t: Float) -> (Int, Float){ x = t return (u, x) } }