struct Point{
  x: i32,
  y: i32
}
impl Point{
  fn move_x(self){
    self.x
  }
  fn move_x_rfc(self::M)
  where M: self::x
  {
     self.x
  }
  fn move_y(self){
    self.y
  }
  fn move_y_rfc(self::M)
   where M:: self.y
  {
     self.y
  }
}
// 更复杂的嵌套类型
struct Inner{
  f1: String,
  f2: String
}
struct Data{
  x: i32,
  inner: Inner
}
impl Data{
  fn move_x_inner_f1(self::M) -> (i32, String)
 ...