AnyEquatable.swift

struct AnyEquatable: Equatable {
    static func ==(lhs: AnyEquatable, rhs: AnyEquatable) -> Bool {
        return lhs.isEqual(rhs.value)
    }
    
    private let isEqual: (Any) -> Bool
    private let value: Any
    
    init<T: Equatable>(_ value: T) {
        self.value = value
        isEqual = { ($0 as? T) == value }
    }
}

let x1 = AnyEquatable(1)
let x2 = AnyEquatable(1)
assert(x1 == x2)

let y1 = AnyEquatable(1)
let y2 = AnyEquatable(2)
assert(y1 != y2)

let z1 = AnyEquatable(1)
let z2 = AnyEquatable("1")
assert(z1 != z2)