slice.rs

 1// SPDX-License-Identifier: GPL-2.0
 2
 3//! Additional (and temporary) slice helpers.
 4
 5/// Extension trait providing a portable version of [`as_flattened`] and
 6/// [`as_flattened_mut`].
 7///
 8/// In Rust 1.80, the previously unstable `slice::flatten` family of methods
 9/// have been stabilized and renamed from `flatten` to `as_flattened`.
10///
11/// This creates an issue for as long as the MSRV is < 1.80, as the same functionality is provided
12/// by different methods depending on the compiler version.
13///
14/// This extension trait solves this by abstracting `as_flatten` and calling the correct method
15/// depending on the Rust version.
16///
17/// This trait can be removed once the MSRV passes 1.80.
18///
19/// [`as_flattened`]: https://doc.rust-lang.org/std/primitive.slice.html#method.as_flattened
20/// [`as_flattened_mut`]: https://doc.rust-lang.org/std/primitive.slice.html#method.as_flattened_mut
21#[cfg(not(CONFIG_RUSTC_HAS_SLICE_AS_FLATTENED))]
22pub trait AsFlattened<T> {
23    /// Takes a `&[[T; N]]` and flattens it to a `&[T]`.
24    ///
25    /// This is an portable layer on top of [`as_flattened`]; see its documentation for details.
26    ///
27    /// [`as_flattened`]: https://doc.rust-lang.org/std/primitive.slice.html#method.as_flattened
28    fn as_flattened(&self) -> &[T];
29
30    /// Takes a `&mut [[T; N]]` and flattens it to a `&mut [T]`.
31    ///
32    /// This is an portable layer on top of [`as_flattened_mut`]; see its documentation for details.
33    ///
34    /// [`as_flattened_mut`]: https://doc.rust-lang.org/std/primitive.slice.html#method.as_flattened_mut
35    fn as_flattened_mut(&mut self) -> &mut [T];
36}
37
38#[cfg(not(CONFIG_RUSTC_HAS_SLICE_AS_FLATTENED))]
39impl<T, const N: usize> AsFlattened<T> for [[T; N]] {
40    #[allow(clippy::incompatible_msrv)]
41    fn as_flattened(&self) -> &[T] {
42        self.flatten()
43    }
44
45    #[allow(clippy::incompatible_msrv)]
46    fn as_flattened_mut(&mut self) -> &mut [T] {
47        self.flatten_mut()
48    }
49}