Returning results and options in Rust and Swift

error.rs

enum TestErr {
    MuchFatalSuchWow,
}

fn return_result() -> Result<String, TestErr> {
    // String::new() // doesn't work
    // TestErr::MuchFatalSuchWow // doesn't work
    Err(TestErr::MuchFatalSuchWow)
}

fn return_option() -> Option<String> {
    // String::new() // doesn't work
    None
}

error.swift

// I wish Swift had a built-in Result type :/
enum Result<T,E> {
    case ok(T)
    case err(E)
}

enum TestError: Error { // actually being an Error is optional for this use-case
    case muchFatalSuchWow
}

func return_result() -> Result<String, TestError> {
    // return String() // doesn't work
    // return TestError.muchFatalSuchWow // doesn't work
    return .err(.muchFatalSuchWow)
}

func return_optional() -> String? {
    return "" // this works
    // .some("") // also works
    // return .none // also works
    // return nil // also works
}