Overload struct operators

Reserved inherent method names define operators for a struct. For example, binary + calls add(self, other), while unary - calls neg(self).

Comparison overloads and not return bool. Compound assignment uses the same overloaded binary operation before storing the result.

struct Point { x: int, y: int }

impl Point {
  fn add(self: Point, other: Point) -> Point {
    Point { x: self.x + other.x, y: self.y + other.y }
  }
}

fn main() {
  let point = Point { x: 1, y: 2 } + Point { x: 4, y: 5 }
  println("${point.x},${point.y}")
}