# Trait core::marker::Unsize [−] [src]

    #[lang = "unsize"]
    pub trait Unsize<T: ?Sized> { }

🔬 This is a nightly-only experimental API. (`unsize` #27732)

Types that can be "unsized" to a dynamically-sized type.

For example, the sized array type `[i8; 2]` implements `Unsize<[i8]>` and `Unsize<fmt::Debug>`.

All implementations of `Unsize` are provided automatically by the compiler.

`Unsize` is implemented for:

- `[T; N]` is `Unsize<[T]>`
- `T` is `Unsize<Trait>` when `T: Trait`
- `Foo<..., T, ...>` is `Unsize<Foo<..., U, ...>>` if:
  - `T: Unsize<U>`
  - Foo is a struct
  - Only the last field of `Foo` has a type involving `T`
  - `T` is not part of the type of any other fields
  - `Bar<T>: Unsize<Bar<U>>`, if the last field of `Foo` has type `Bar<T>`

`Unsize` is used along with `ops::CoerceUnsized` to allow "user-defined" containers such as `rc::Rc` to contain dynamically-sized types. See the DST coercion RFC and [the nomicon entry on coercion][nomicon-coerce] for more details.

## Implementors

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)