PropertyWrapperImplicitlyOptionalOverwrite.swift

import Foundation

var value: Any = "value"

@propertyWrapper
struct Wrapper<Value> {
    private let defaultValue: Value

    init(defaultValue: Value) {
        self.defaultValue = defaultValue
    }

    var wrappedValue: Value {
        get {
            (value as? Value) ?? defaultValue
        }
        set {
            value = newValue
        }
    }
}

final class Playground {
    @Wrapper(defaultValue: nil)
    var explicitlyOptional: String?

    @Wrapper(defaultValue: nil)
    var implicitlyOptional: String

    @Wrapper(defaultValue: "NonOptional")
    var nonOptional: String

    func printExplicitlyOptionalType() {
        print(type(of: self.explicitlyOptional))
    }

    func printImplicitlyOptionalType() {
        print(type(of: self.implicitlyOptional))
    }

    func printNonOptionalType() {
        print(type(of: self.nonOptional))
    }

}

let playground = Playground()
playground.printExplicitlyOptionalType()   // Optional<String>
playground.printImplicitlyOptionalType()   // Optional<String>
playground.printNonOptionalType()  // String