swift, troubles with generic parameters and constraints

Question

I'm writing some tests and mocks for my product but I'm having troubles with generic parameters and constraints...

enum ApiResult<Success, Failure> where Failure: Error {
    case success(Success)
    case failure(Failure)
    case disconnected
}

var askedDecodableApiResult: ApiResult<Decodable, Error> = .disconnected

func complete<T>(callback: @escaping (ApiResult<T, Error>) -> Void) where T: Decodable {
    callback(askedDecodableApiResult) //  Cannot convert value of type 'ApiResult<Decodable, Error>' to expected argument type 'ApiResult<T, Error>'
}

I'm lost with that error. What should I do to be able to send in my callback the pre-defined answer ? In the end, I want to be able to give my askedDecodableApiResult any ApiResult sporting a value that either inherits from Decodable or inherits from Error.

I need your help, thanks in advance :)