Move CoerceUnsized to module.
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@ -155,6 +155,7 @@ mod index;
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mod place;
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mod range;
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mod try;
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mod unsize;
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use self::arith::{Add, Sub, Mul, Div, Rem, Neg};
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@ -190,7 +191,8 @@ pub use self::try::Try;
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#[unstable(feature = "placement_new_protocol", issue = "27779")]
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pub use self::place::{Place, Placer, InPlace, Boxed, BoxPlace};
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use marker::Unsize;
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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pub use self::unsize::CoerceUnsized;
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/// The `Drop` trait is used to run some code when a value goes out of scope.
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/// This is sometimes called a 'destructor'.
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@ -281,71 +283,3 @@ pub trait Drop {
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#[stable(feature = "rust1", since = "1.0.0")]
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fn drop(&mut self);
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}
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/// Trait that indicates that this is a pointer or a wrapper for one,
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/// where unsizing can be performed on the pointee.
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///
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/// See the [DST coercion RfC][dst-coerce] and [the nomicon entry on coercion][nomicon-coerce]
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/// for more details.
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///
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/// For builtin pointer types, pointers to `T` will coerce to pointers to `U` if `T: Unsize<U>`
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/// by converting from a thin pointer to a fat pointer.
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///
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/// For custom types, the coercion here works by coercing `Foo<T>` to `Foo<U>`
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/// provided an impl of `CoerceUnsized<Foo<U>> for Foo<T>` exists.
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/// Such an impl can only be written if `Foo<T>` has only a single non-phantomdata
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/// field involving `T`. If the type of that field is `Bar<T>`, an implementation
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/// of `CoerceUnsized<Bar<U>> for Bar<T>` must exist. The coercion will work by
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/// by coercing the `Bar<T>` field into `Bar<U>` and filling in the rest of the fields
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/// from `Foo<T>` to create a `Foo<U>`. This will effectively drill down to a pointer
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/// field and coerce that.
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///
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/// Generally, for smart pointers you will implement
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/// `CoerceUnsized<Ptr<U>> for Ptr<T> where T: Unsize<U>, U: ?Sized`, with an
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/// optional `?Sized` bound on `T` itself. For wrapper types that directly embed `T`
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/// like `Cell<T>` and `RefCell<T>`, you
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/// can directly implement `CoerceUnsized<Wrap<U>> for Wrap<T> where T: CoerceUnsized<U>`.
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/// This will let coercions of types like `Cell<Box<T>>` work.
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///
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/// [`Unsize`][unsize] is used to mark types which can be coerced to DSTs if behind
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/// pointers. It is implemented automatically by the compiler.
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///
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/// [dst-coerce]: https://github.com/rust-lang/rfcs/blob/master/text/0982-dst-coercion.md
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/// [unsize]: ../marker/trait.Unsize.html
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/// [nomicon-coerce]: ../../nomicon/coercions.html
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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#[lang="coerce_unsized"]
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pub trait CoerceUnsized<T> {
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// Empty.
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}
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// &mut T -> &mut U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a mut U> for &'a mut T {}
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// &mut T -> &U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, 'b: 'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b mut T {}
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// &mut T -> *mut U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for &'a mut T {}
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// &mut T -> *const U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for &'a mut T {}
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// &T -> &U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, 'b: 'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
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// &T -> *const U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for &'a T {}
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// *mut T -> *mut U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
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// *mut T -> *const U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *mut T {}
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// *const T -> *const U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *const T {}
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@ -0,0 +1,79 @@
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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use marker::Unsize;
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/// Trait that indicates that this is a pointer or a wrapper for one,
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/// where unsizing can be performed on the pointee.
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///
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/// See the [DST coercion RfC][dst-coerce] and [the nomicon entry on coercion][nomicon-coerce]
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/// for more details.
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///
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/// For builtin pointer types, pointers to `T` will coerce to pointers to `U` if `T: Unsize<U>`
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/// by converting from a thin pointer to a fat pointer.
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///
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/// For custom types, the coercion here works by coercing `Foo<T>` to `Foo<U>`
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/// provided an impl of `CoerceUnsized<Foo<U>> for Foo<T>` exists.
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/// Such an impl can only be written if `Foo<T>` has only a single non-phantomdata
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/// field involving `T`. If the type of that field is `Bar<T>`, an implementation
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/// of `CoerceUnsized<Bar<U>> for Bar<T>` must exist. The coercion will work by
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/// by coercing the `Bar<T>` field into `Bar<U>` and filling in the rest of the fields
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/// from `Foo<T>` to create a `Foo<U>`. This will effectively drill down to a pointer
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/// field and coerce that.
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///
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/// Generally, for smart pointers you will implement
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/// `CoerceUnsized<Ptr<U>> for Ptr<T> where T: Unsize<U>, U: ?Sized`, with an
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/// optional `?Sized` bound on `T` itself. For wrapper types that directly embed `T`
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/// like `Cell<T>` and `RefCell<T>`, you
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/// can directly implement `CoerceUnsized<Wrap<U>> for Wrap<T> where T: CoerceUnsized<U>`.
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/// This will let coercions of types like `Cell<Box<T>>` work.
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///
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/// [`Unsize`][unsize] is used to mark types which can be coerced to DSTs if behind
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/// pointers. It is implemented automatically by the compiler.
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///
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/// [dst-coerce]: https://github.com/rust-lang/rfcs/blob/master/text/0982-dst-coercion.md
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/// [unsize]: ../marker/trait.Unsize.html
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/// [nomicon-coerce]: ../../nomicon/coercions.html
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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#[lang="coerce_unsized"]
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pub trait CoerceUnsized<T> {
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// Empty.
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}
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// &mut T -> &mut U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a mut U> for &'a mut T {}
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// &mut T -> &U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, 'b: 'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b mut T {}
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// &mut T -> *mut U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for &'a mut T {}
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// &mut T -> *const U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for &'a mut T {}
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// &T -> &U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, 'b: 'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
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// &T -> *const U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for &'a T {}
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// *mut T -> *mut U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
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// *mut T -> *const U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *mut T {}
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// *const T -> *const U
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#[unstable(feature = "coerce_unsized", issue = "27732")]
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impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *const T {}
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