1 // Copyright 2021 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 use core::mem::MaybeUninit;
16 use core::pin::Pin;
17
18 use crate::move_ref::AsMove;
19 use crate::move_ref::MoveRef;
20 use crate::new;
21 use crate::new::New;
22 use crate::slot;
23
24 /// A move constructible type: a destination-aware `Clone` that destroys the
25 /// moved-from value.
26 ///
27 /// # Safety
28 ///
29 /// After [`MoveNew::move_new()`] is called:
30 /// - `src` should be treated as having been destroyed.
31 /// - `this` must have been initialized.
32 pub unsafe trait MoveNew: Sized {
33 /// Move-construct `src` into `this`, effectively re-pinning it at a new
34 /// location.
35 ///
36 /// # Safety
37 ///
38 /// The same safety requirements of [`New::new()`] apply, but, in addition,
39 /// `*src` must not be used after this function is called, because it has
40 /// effectively been destroyed.
move_new( src: Pin<MoveRef<Self>>, this: Pin<&mut MaybeUninit<Self>>, )41 unsafe fn move_new(
42 src: Pin<MoveRef<Self>>,
43 this: Pin<&mut MaybeUninit<Self>>,
44 );
45 }
46
47 /// Returns a [`New`] that forwards to [`MoveNew`].
48 ///
49 /// ```
50 /// # use moveit::{MoveRef, moveit, new};
51 /// let foo = Box::new(42);
52 /// moveit! {
53 /// let bar = &move foo;
54 /// let baz = new::mov(bar);
55 /// }
56 /// ```
57 #[inline]
mov<P>(ptr: P) -> impl New<Output = P::Target> where P: AsMove, P::Target: MoveNew,58 pub fn mov<P>(ptr: P) -> impl New<Output = P::Target>
59 where
60 P: AsMove,
61 P::Target: MoveNew,
62 {
63 unsafe {
64 new::by_raw(move |this| {
65 MoveNew::move_new(ptr.as_move(slot!(#[dropping])), this);
66 })
67 }
68 }
69