1 # `unsized_tuple_coercion`
3 The tracking issue for this feature is: [#42877]
5 [#42877]: https://github.com/rust-lang/rust/issues/42877
7 ------------------------
9 This is a part of [RFC0401]. According to the RFC, there should be an implementation like this:
11 ```rust,ignore (partial-example)
12 impl<..., T, U: ?Sized> Unsized<(..., U)> for (..., T) where T: Unsized<U> {}
15 This implementation is currently gated behind `#[feature(unsized_tuple_coercion)]` to avoid insta-stability. Therefore you can use it like this:
18 #![feature(unsized_tuple_coercion)]
21 let x : ([i32; 3], [i32; 3]) = ([1, 2, 3], [4, 5, 6]);
22 let y : &([i32; 3], [i32]) = &x;
23 assert_eq!(y.1[0], 4);
27 [RFC0401]: https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md