Polymorphism with Swift Value Types: Mind Blown

PolymorphicValueTypes.swift

protocol Thing {
    func foo()
}

extension Thing {
    func foo() {
        print("just a thing")
    }
}

struct Sprocket: Thing {
    func foo() {
        print("sprocket")
    }
}

struct Widget: Thing {
    func foo() {
        print("widget")
    }
}

enum Instrument: Thing {
    case trombone
    
    func foo() {
        print("not even a struct!?")
    }
}

extension Int: Thing {
    func foo() {
        print("now you're trolling me!!!")
    }
}

struct Boring: Thing {
    
}

let things: [Thing] = [Sprocket(), Widget(), Boring(), Instrument.trombone, 12]
things.forEach { $0.foo() }