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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
|
