trait Add<R = Self>
    type Output = Self

    fn add(other: R) -> Self::Output
end

intrinsic class Int end
intrinsic class Double end

impl Add for Int
    fn add(other: Self) -> Self
        self + other
    end
end

impl Add<Double> for Int
    type Output = Double

    fn add(other: Double) -> Double
        self + other
    end
end

impl Add for Double
    fn add(other: Self) -> Self
        self + other
    end
end

impl Add<Int> for Double
    fn add(other: Int) -> Self
        self + other
    end
end

fn add_rough_pi(a: impl Add<Double>) -> Double = a + 3.14

fn concat<T: impl Add<U>, U>(a: T, b: U) -> T::Output
    a + b
end

fn main()
    let x = add_rough_pi(3)
    println(x) // 6.14
    let y = concat(1, 2) // 3
    let z = concat("Hello, ", "World!") // "Hello, World!"
end