Custom RawRepresentable support

[basememara]

I ran into a situation where the compiler allowed me to implement a custom RawRepresentable type but crashed at runtime:

struct TestCustomRepresented: RawRepresentable, UserDefaultsSerializable {
    var rawValue: [String: TestFruit]

    init(rawValue: [String: TestFruit]) {
        self.rawValue = rawValue
    }
}

final class TestSettings {
    @WrappedDefaultOptional(keyName: "customRawRepresented", userDefaults: store)
    var customRawRepresented: TestCustomRepresented?
}

When I ran this and tried saving a value to it, I got this crash:

settings.customRawRepresented = TestCustomRepresented(rawValue: ["key1": .apple])

// =>

libc++abi: terminating with uncaught exception of type NSException
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Attempt to insert non-property list object {
    key1 = "FoilTests.TestFruit.apple";
} for key customRawRepresented'
terminating with uncaught exception of type NSException

What I ended up doing is fine-tuning the conditional bounds for Self.RawValue conformance of RawRepresentable and adjusting the implementation:

// From this:
extension UserDefaultsSerializable where Self: RawRepresentable {
    public var storedValue: RawValue { self.rawValue }

    public init(storedValue: RawValue) {
        self = Self(rawValue: storedValue)!
    }
}

// To this:
extension UserDefaultsSerializable where Self: RawRepresentable, Self.RawValue: UserDefaultsSerializable {
    public var storedValue: RawValue.StoredValue { self.rawValue.storedValue }

    public init(storedValue: RawValue.StoredValue) {
        self = Self(rawValue: Self.RawValue(storedValue: storedValue))!
    }
}

This makes sense to leverage RawRepresentable this way since according to the docs, RawRepresentable was designed to interoperate with legacy systems, which UserDefaults could be considered:

Using the raw value of a conforming type streamlines interoperation with Objective-C and legacy APIs..

Doing this opened some interesting doors to UserDefaults while allowing existing RawRepresentable conformers to remain unchanged:

struct TestCustomRepresented: RawRepresentable, UserDefaultsSerializable {
    var rawValue: [String: TestFruit]

    init(rawValue: [String: TestFruit]) {
        self.rawValue = rawValue
    }
}

extension TestCustomRepresented {
    enum Key: String {
        case key1, key2, key3
    }

    subscript(_ key: Key) -> TestFruit? {
        get { rawValue[key.rawValue] }
        set { rawValue[key.rawValue] = newValue }
    }
}

settings.customRawRepresented[.key2] = .orange

[jessesquires]

This is great 💯 🎉 Nice find @basememara!

[jessesquires]

Requesting changes to add a changelog entry for this.

I made some updates in #11, so you'll want to rebase on main first and then just follow the pattern in the changelog. 😊

[basememara]

Cool updated the changelog, let me know if you need any other changes

[jessesquires]

🎉