Code shared from the Rust Playground

playground.rs

#![feature(generic_associated_types)]
use core::ops::Index;
use core::ops::IndexMut;


pub trait IndexRef<Idx: ?Sized> {
    type Output<'a>: ?Sized;
    fn index(&self, index: Idx) -> &Self::Output<'_>;
}

pub trait IndexMutRef<Idx: ?Sized>: IndexRef<Idx> {
    fn index_mut(&mut self, index: Idx) -> &mut Self::Output<'_>;
}

pub trait IndexVal<Idx: ?Sized> {
    type Output<'a>: ?Sized;
    fn index(&self, index: Idx) -> Self::Output<'_>;
}

impl<T: Index<Idx>, Idx> IndexRef<Idx> for T {
    type Output<'a> = <Self as Index<Idx>>::Output;
    
    fn index(&self, index: Idx) -> &Self::Output<'_> {
        <Self as Index<Idx>>::index(self, index)
    }
}

impl<T: IndexMut<Idx>, Idx> IndexMutRef<Idx> for T {
    fn index_mut(&mut self, index: Idx) -> &mut Self::Output<'_> {
        <Self as IndexMut<Idx>>::index_mut(self, index)
    }
}