--retain-codable-properties does not retain initializers

[ileitch]

[ileitch]

Stupid of me not to give context on this. I'm not sure what the issue was that I saw, but an unused memberwise initializer on a Codable struct is reasonable to identify as unused, as it can be removed without causing build errors.

import Foundation

public struct FixtureStruct14: Codable {
    let unused: Int

    init(unused: Int) { // unused
        self.unused = unused
    }
}