message: Implement RefNum more generically
diff: @@ -89,9 +89,9 @@ impl<T> NumRef for T where T: Num + for<'r> NumOps<&'r T> {}
  /// The trait for references which implement numeric operations, taking the
  /// second operand either by value or by reference.
  ///
  -/// This is automatically implemented for all `&T` implementing the operators.
  +/// This is automatically implemented for types which implement the operators.
  pub trait RefNum<Base>: NumOps<Base, Base> + for<'r> NumOps<&'r Base, Base> {}
  -impl<'a, T> RefNum<T> for &'a T where &'a T: NumOps<T, T> + for<'r> NumOps<&'r T, T> {}
  +impl<T, Base> RefNum<Base> for T where T: NumOps<Base, Base> + for<'r> NumOps<&'r Base, Base> {}
  /// The trait for types implementing numeric assignment operators (like `+=`).
  ///
  