Implementation of an Optional protocol for Swift using Swift 5.3 enum case as protocol witness

OptionalProtocol.swift

public protocol OptionalProtocol: ExpressibleByNilLiteral {
     associatedtype Wrapped
     var wrapped: Wrapped? { get }
     static var none: Self { get }
     static func some(_ newValue: Wrapped) -> Self
     func map<U>(_ f: (Wrapped) throws -> U) rethrows -> U?
     func flatMap<U>(_ f: (Wrapped) throws -> U?) rethrows -> U?
 }

 extension Optional: OptionalProtocol {
     public var wrapped: Wrapped? { return self }
 }

Makes this kind of code possible:

extension Sequence where Element: OptionalProtocol {
     public func compacted() -> [Element.Wrapped] {
         compactMap(\.wrapped)
     }
 }