switch.swift

// Compile with `swiftc switch.swift`

enum A {
	case A(Int)
	case B(Bool)
	case C
	case D
}

enum B {
	case A
	case B
}

func s(a: A, b: B) {
	// error: switch must be exhaustive, consider adding a default clause
	// WTF
	switch (a, b) {
		case let (.A(i), .A):
			break
		case let (.A(i), .B):
			break

		case let (.B(boolean), b):
			break

		case (.C, _), (.D, _):
			break
	}
}

Looks like it can’t infer b’s cases when a is either .C or .D, only this works:

func s(a: A, b: B) {
    switch (a, b) {
    case let (.A(i), .A):
        print(i)
        break
    case let (.A(i), .B):
        print(i)
        break
    case let (.B(boolean), .A):
        print(boolean)
        break
    case let (.B(boolean), .B):
        print(boolean)
        break
    case (.C, B.A):
        break
    case (.C, B.B):
        break
    case (.D, B.A):
        break
    case (.D, B.B):
        break
    }
}

Note: this was done in Swift 2.0 beta 5.