Consider modifying the Mul<Self, Output = Self> bound on WrappingMul

[aerkiaga]

Currently, the WrappingMul trait has a Mul<Self, Output = Self> bound on it. This is incompatible with compile-time large numeric types types that use const generics to increase their width upon multiplication rather than panicking or overflowing, but which may still want to provide a wrapping version of the operation. I propose removing the Output = Self associated type bound from it.

This is not a breaking change.

[cuviper]

It is a breaking change, because users can no longer rely on that equivalence.

use num_traits::WrappingMul;

pub trait WrappingMul2: Sized + std::ops::Mul<Self> {
    fn wrapping_mul(&self, v: &Self) -> Self;
}

fn mul<T: WrappingMul>(x: T, y: T) -> T {
    // We know Mul::Output is T
    x * y
}

fn mul2<T: WrappingMul2>(x: T, y: T) -> T {
    x * y
//  ^^^^^ expected type parameter `T`, found associated type
}

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=ea08daf166ec856c0470515b7e9e51d5

[dzmitry-lahoda]

for somebody it is breaking change, for others, hopefully, we can see next major version bump in optimistic roadmap?