Smashables and Values

gistfile1.swift

//: Playground - noun: a place where people can play

protocol HeterogenousEquatable
{
    func isEqual(other: HeterogenousEquatable) -> Bool
}

protocol Value: HeterogenousEquatable
{
    
}

protocol Smashable {
    func valueBySmashing​OtherValue(value: Value) -> Value
}

struct Bar : Value
{
}

struct Baz : Value, Equatable
{
}

func ==(lhs: Baz, rhs: Baz) -> Bool
{
    return true // exercise for the reader
}


extension Value where Self: Equatable
{
    func isEqual(other: HeterogenousEquatable) -> Bool {
        guard let selfOther = other as? Self else { return false }
        return selfOther == self
    }
}

struct Foo : Smashable
{
    func valueBySmashing​OtherValue(value: Value) -> Value {
        return Bar()
    }
    
    func valueBySmashing​OtherValue(value: Value) -> Bar {
        return Bar()
    }
    
    func test() {
        let f = Foo()
        let z = Baz()
        let b: Bar = f.valueBySmashing​OtherValue(v)
        
        let ok = v == Bar()
        let ok2 = z == Baz()
    }
}

Updated, but this one crashes the compiler so I'm not sure it actually works.

Hm, this one doesn't crash: https://gist.github.com/andymatuschak/a40c4c699c0abdd704ce