Result+casting.swift

import Swift

extension Result {
    func casting<NewSuccess, NewFailure>() -> Result<NewSuccess, NewFailure>? {
        switch self {
        case .success(let success as NewSuccess) where Failure.self is NewFailure.Type: return .success(success)
        case .failure(let failure as NewFailure) where Success.self is NewSuccess.Type: return .failure(failure)
        default: return nil
        }
    }
}