I made a bunch of functions and an enumeration, that together allow me to write something like a switch expression. It's not as powerful as Swift switch statements, since it's lacking pattern matching and I don't intend to use this in real code, it was just an experiment. Here is what I got:

enum Caze<T: ForwardIndexType where T: Equatable> {
    case RangeCaze(Range<T>)
    case ArrayCaze([T])
    
    func contains(elem: T) -> Bool {
        switch self {
        case let .RangeCaze(r):
            return r.contains(elem)
        case let .ArrayCaze(arr):
            return arr.contains(elem)
        }
    }
}


func caze<T: ForwardIndexType, R where T: Equatable>(vals: T..., @autoclosure(escaping) ret f: () -> R) -> (Caze<T>, () -> R) {
    return (.ArrayCaze(vals), f)
}

func caze<T: ForwardIndexType, R where T: Equatable>(vals: Range<T>, @autoclosure(escaping) ret f: () -> R) -> (Caze<T>, () -> R) {
    return (.RangeCaze(vals), f)
}

func caze<T: Equatable, R>(vals: T..., @autoclosure(escaping) ret f: () throws -> R) -> ([T], () throws -> R) {
    return (vals, f)
}


func schwitch<T: ForwardIndexType, R where T: Equatable>(value: T, _ cases: (Caze<T>, () -> R)..., @autoclosure def: () throws -> R) rethrows -> R {
    for (vals, f) in cases {
        if vals.contains(value) {
            return f()
        }
    }
    return try def()
}

func schwitch<T: Equatable, R>(value: T, _ cases: ([T], () -> R)..., @autoclosure def: () throws -> R) rethrows -> R {
    for (vals, f) in cases {
        if vals.contains(value) {
            return f()
        }
    }
    return try def()
}

This allows me to write code like:

schwitch(5, // results in "lol"
    caze(0, ret: "hello"),
    caze(1, 2, ret: "test"),
    caze(3..<7, ret: "lol"),
    def: "nop")

schwitch("helloo", //results in "nop"
    caze("hello", "Hello", ret: "test"),
    def: "nop")

I think there are a few problems with this though.

1. There is quite a bit of code duplication due to a few nearly identical functions being needed
2. The closure sent to the caze functions are escaping, though they are intended to never actually escape beyond a very defined scope.
3. If code in a caze function throws, it doesn't get rethrown

Are there any ways to improve on these 3 points and are there any other things that I missed or could have done better?