typeCheck.swift

import Foundation

// Make 5 pattern base types

class A {}
protocol B {}
protocol C: class {}
@objc protocol D {}
protocol E: NSObjectProtocol {}

// Make container protocol

protocol Container {
    associatedtype Wrapped
}

// If Container conforms to Wrapped then return true.
func typeCheckShouldBeSuccess<T: Container>(_ type: T.Type) -> Bool {
    return T.self is T.Wrapped.Type
}

// Always false because T.self is type and not conforms to value of Wrapped.
func typeCheckShouldBeFailure<T: Container>(_ type: T.Type) -> Bool {
    return T.self is T.Wrapped
}

// Make Container implementation that extends of base type, and Wrapped is base type.

class ContainerA: A, Container {
    typealias Wrapped = A
}
class ContainerB: B, Container {
    typealias Wrapped = B
}
class ContainerC: C, Container {
    typealias Wrapped = C
}
class ContainerD: D, Container {
    typealias Wrapped = D
}
class ContainerE: NSObject, E, Container {
    typealias Wrapped = E
}

// Case of A is fine.

let r01 = ContainerA.self is ContainerA.Wrapped.Type    // true. ContainerA is subclass of A
let r02 = typeCheckShouldBeSuccess(ContainerA.self)     // true. Should be same of r01
let r03 = ContainerA.self is ContainerA.Wrapped         // false. ContainerA.self is Type, not value of A.
let r04 = typeCheckShouldBeFailure(ContainerA.self)     // false. Should be same of r03

// Cases of B~E are (maybe) wrong.

let r05 = ContainerB.self is ContainerB.Wrapped.Type    // true. ok.
let r06 = typeCheckShouldBeSuccess(ContainerB.self)     // false. wrong. It should be same of r05.
let r07 = ContainerB.self is ContainerB.Wrapped         // false. ok.
let r08 = typeCheckShouldBeFailure(ContainerB.self)     // false. ok.

let r09 = ContainerC.self is ContainerC.Wrapped.Type    // true. ok.
let r10 = typeCheckShouldBeSuccess(ContainerC.self)     // false. wrong. It should be same of r09.
let r11 = ContainerC.self is ContainerC.Wrapped         // false. ok.
let r12 = typeCheckShouldBeFailure(ContainerC.self)     // true. wrong. It should be same of r11.

let r13 = ContainerD.self is ContainerD.Wrapped.Type    // true. ok.
let r14 = typeCheckShouldBeSuccess(ContainerD.self)     // false. wrong. It should be same of r13.
let r15 = ContainerD.self is ContainerD.Wrapped         // true. wrong. ContainerD.self is Type, not value of D.
let r16 = typeCheckShouldBeFailure(ContainerD.self)     // true. wrong. 

let r17 = ContainerE.self is ContainerE.Wrapped.Type    // true. ok.
let r18 = typeCheckShouldBeSuccess(ContainerE.self)     // false. wrong. It should be same of r17.
let r19 = ContainerE.self is ContainerE.Wrapped         // false. ok.
let r20 = typeCheckShouldBeFailure(ContainerE.self)     // true. wrong. It should be same of r19.