message: Relax trait bound for Sub of matrices
  Change from SubAssign to Sub as a bound for matrix subtraction.
diff: @@ -1204,7 +1204,8 @@ where
  impl<'a, 'b, N, I, IS1, DS1, IS2, DS2> Sub<&'b CsVecBase<IS2, DS2, N, I>>
  for &'a CsVecBase<IS1, DS1, N, I>
  where
  - N: Num + Clone + for<'r> std::ops::SubAssign<&'r N>,
  + N: Num,
  + for<'r> &'r N: std::ops::Sub<Output = N>,
  I: SpIndex,
  IS1: Deref<Target = [I]>,
  DS1: Deref<Target = [N]>,
  @@ -1214,16 +1215,15 @@ where
  type Output = CsVecI<N, I>;
  fn sub(self, rhs: &CsVecBase<IS2, DS2, N, I>) -> Self::Output {
  - binop::csvec_binop(self.view(), rhs.view(), |x, y| {
  - let mut res = x.clone();
  - res -= y;
  - res
  - })
  - .unwrap()
  + binop::csvec_binop(self.view(), rhs.view(), |x, y| x - y).unwrap()
  }
  }
  -impl<N: Num + Clone + Neg<Output = N>, I: SpIndex> Neg for CsVecI<N, I> {
  +impl<N, I> Neg for CsVecI<N, I>
  +where
  + N: Num + Clone + Neg<Output = N>,
  + I: SpIndex,
  +{
  type Output = Self;
  fn neg(mut self) -> Self::Output {
  