duplicates:

• SR-3779 Program with struct nested in generic struct crashes because of “cyclic metadata dependency”

Issue Description:

public struct Cyclic<T> {
    enum Nested {
        case a(T), b
    }
 
    let state: Nested
 
    init(_ value: T) {
        state = .a(value)
    }
}
 
Cyclic(1)

This produces the following runtime error:

GenericCache(0x1174e4330): cyclic metadata dependency detected, aborting

I have a vary vague feeling why the nested (implicitly generic) enum somehow is responsible for the recursive type dependency.

On the other hand, the following code works as expected:

enum Outer<T> {
    case a(T), b
}

public struct Acyclic<T> {

    let state: Outer<T>

    init(_ value: T) {
        state = .a(value)
    }
}

let _ = Acyclic(1)

This makes me think the compiler should be able to solve the metadata dependency, at least in this simple case.