Require Neg for Complex conj and inv

If T is an unsigned integer type, these methods are guaranteed to
overflow unless the result is actually real, so we should disallow
them for the same reason that Neg was removed from these types.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

src/complex.rs

@@ -56,11 +56,13 @@ impl<T: Clone + Num> Complex<T> {
     pub fn unscale(&self, t: T) -> Complex<T> {
         Complex::new(self.re.clone() / t.clone(), self.im.clone() / t)
     }
+}
 
+impl<T: Clone + Num + Neg<Output = T>> Complex<T> {
     /// Returns the complex conjugate. i.e. `re - i im`
     #[inline]
     pub fn conj(&self) -> Complex<T> {
-        Complex::new(self.re.clone(), T::zero() - self.im.clone())
+        Complex::new(self.re.clone(), -self.im.clone())
     }
 
     /// Returns `1/self`
@@ -68,7 +70,7 @@ impl<T: Clone + Num> Complex<T> {
     pub fn inv(&self) -> Complex<T> {
         let norm_sqr = self.norm_sqr();
         Complex::new(self.re.clone() / norm_sqr.clone(),
-                    T::zero() - self.im.clone() / norm_sqr)
+                     -self.im.clone() / norm_sqr)
     }
 }