| The Unsize trait should not be implemented directly. All implementations of |
| Unsize are provided automatically by the compiler. |
| |
| Erroneous code example: |
| |
| ```compile_fail,E0328 |
| #![feature(unsize)] |
| |
| use std::marker::Unsize; |
| |
| pub struct MyType; |
| |
| impl<T> Unsize<T> for MyType {} |
| ``` |
| |
| If you are defining your own smart pointer type and would like to enable |
| conversion from a sized to an unsized type with the |
| [DST coercion system][RFC 982], use [`CoerceUnsized`] instead. |
| |
| ``` |
| #![feature(coerce_unsized)] |
| |
| use std::ops::CoerceUnsized; |
| |
| pub struct MyType<T: ?Sized> { |
| field_with_unsized_type: T, |
| } |
| |
| impl<T, U> CoerceUnsized<MyType<U>> for MyType<T> |
| where T: CoerceUnsized<U> {} |
| ``` |
| |
| [RFC 982]: https://github.com/rust-lang/rfcs/blob/master/text/0982-dst-coercion.md |
| [`CoerceUnsized`]: https://doc.rust-lang.org/std/ops/trait.CoerceUnsized.html |
