pub trait Boxed { type Data; type Place: BoxPlace<Self::Data>; unsafe fn finalize(filled: Self::Place) -> Self; }
Core trait for the box EXPR
form.
box EXPR
effectively desugars into:
let mut place = BoxPlace::make_place(); let raw_place = Place::pointer(&mut place); let value = EXPR; unsafe { ::std::ptr::write(raw_place, value); Boxed::finalize(place) }
The type of box EXPR
is supplied from its surrounding context; in the above expansion, the result type T
is used to determine which implementation of Boxed
to use, and that <T as Boxed>
in turn dictates determines which implementation of BoxPlace
to use, namely: <<T as Boxed>::Place as BoxPlace>
.
type Data
The kind of data that is stored in this kind of box.
type Place: BoxPlace<Self::Data>
The place that will negotiate the storage of the data.
unsafe fn finalize(filled: Self::Place) -> Self
Converts filled place into final owning value, shifting deallocation/cleanup responsibilities (if any remain), over to returned instance of Self
and forgetting filled
.
impl<T> Boxed for Box<T> type Data = T; type Place = IntermediateBox<T>;
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/ops/trait.Boxed.html