ref_pat_eat_one_layer_2024 - The Rust Unstable Book

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# `ref_pat_eat_one_layer_2024`

The tracking issue for this feature is: #123076

This feature is incomplete and not yet intended for general use.

This implements experimental, Edition-dependent match ergonomics under consideration for inclusion in Rust, allowing `&` patterns in more places. For example:

    #![allow(unused)]
    #![feature(ref_pat_eat_one_layer_2024)]
    #![allow(incomplete_features)]
    fn main() {

    // Tests type equality in a way that avoids coercing `&&T` or `&mut T` to `&T`.
    trait Eq<T> {}
    impl<T> Eq<T> for T {}
    fn has_type<T>(_: impl Eq<T>) {}

    // `&` can match against a `ref` binding mode instead of a reference type:
    let (x, &y) = &(0, 1);
    has_type::<&u8>(x);
    has_type::<u8>(y);

    // `&` can match against `&mut` references:
    let &z = &mut 2;
    has_type::<u8>(z);
    }

For specifics, see the corresponding typing rules for Editions 2021 and earlier and for Editions 2024 and later. For more information on binding modes, see The Rust Reference.

For alternative experimental match ergonomics, see the feature `ref_pat_eat_one_layer_2024_structural`.