Cannot implement Mul with different RHS and/or different Return type on one type

[jeaye]

I wrote this thinking it would be possible, but it turns out it isn't yet. It would be very nice if this could be done.

impl Mul<Quaternion, Quaternion> for Quaternion
{
  fn mul(&self, rhs: &Quaternion) -> Quaternion
  {
    Quaternion::new
    (
      self.w * rhs.x + self.x * self.w + self.y * rhs.z - self.z * rhs.y,
      self.w * rhs.y + self.y * self.w + self.z * rhs.x - self.x * rhs.z,
      self.w * rhs.z + self.z * self.w + self.x * rhs.y - self.y * rhs.x,
      self.w * rhs.w - self.x * self.x - self.y * rhs.y - self.z * rhs.z
    )
  }
}

impl Mul<math::Vec3f, math::Vec3f> for Quaternion
{
  fn mul(&self, rhs: &math::Vec3f) -> math::Vec3f
  {
    let vn = math::Vec3f::new_normalized(rhs);
    let vecq = Quaternion::new(vn.x, vn.y, vn.z, 0.0);
    let resq = (vecq * self.get_conjugate()) * self;

    math::Vec3f::new(resq.x, resq.y, resq.z)
  }
}

impl Mul<Component, Quaternion> for Quaternion
{
  fn mul(&self, rhs: &Component) -> Quaternion
  {
    Quaternion::new
    (
      self.x * *rhs,
      self.y * *rhs,
      self.z * *rhs,
      self.w * *rhs
    )
  }
}

[huonw]

There is a work-around, described here under "what if I want overloading?", but hopefully the code you write will be legal some day.

[huonw]

Triage: dupe of #7590.