Example to cause the Swift compiler to go into an infinite loop

SwiftCompilerInfiniteLoopTest.swift

import Foundation

typealias Mask = UInt64

enum Category: UInt8 {
    case A
    case B
    case C
    case D
    case E
    case F
    case G
    case H
}

extension Mask {
    init(_ category: Category) {
        self = UInt64(1) << UInt64(category.rawValue)
    }
}

extension Mask {
    static let dictionary: [Category: Mask] = [
        .A: Mask(.A) | Mask(.B) | Mask(.C) | Mask(.D) | Mask(.E) | Mask(.F) | Mask(.G) | Mask(.H),
        
        // Comment the line below to have it successfully compile. with these two lines it fails to compile
        .B: Mask(.A) | Mask(.B) | Mask(.C) | Mask(.D) | Mask(.E) | Mask(.F) | Mask(.G) | Mask(.H),
    ]
}

I'm using Xcode 7.2

This is a much simpler example of it happening:

import Foundation

typealias Mask = UInt64

enum Category: UInt8 {
    case A
    case B
    case C
    case D
    case E
    case F
    case G
    case H
}

extension Mask {
    static let dictionary: [Category: Mask] = [
        .A: Mask(.A) | Mask(.B) | Mask(.C) | Mask(.D) | Mask(.E) | Mask(.F) | Mask(.G) | Mask(.H)
    ]
}