cyclic metadata dependency detected, aborting

crash.swift

class C<T> {
    enum E {
        case c(T)
    }
    var e: E?
}

let o = C<Int>() // Crash : cyclic metadata dependency detected, aborting

fixed.swift

class C<T> {
    indirect enum E {
        case c(T)
    }
    var e: E?
}

let o = C<Int>() // :)