1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
|
# pin-project
[](https://crates.io/crates/pin-project)
[](https://docs.rs/pin-project)
[](#license)
[](https://www.rust-lang.org)
[](https://github.com/taiki-e/pin-project/actions)
A crate for safe and ergonomic [pin-projection].
## Usage
Add this to your `Cargo.toml`:
```toml
[dependencies]
pin-project = "1"
```
*Compiler support: requires rustc 1.37+*
## Examples
[`#[pin_project]`][`pin_project`] attribute creates projection types
covering all the fields of struct or enum.
```rust
use pin_project::pin_project;
use std::pin::Pin;
#[pin_project]
struct Struct<T, U> {
#[pin]
pinned: T,
unpinned: U,
}
impl<T, U> Struct<T, U> {
fn method(self: Pin<&mut Self>) {
let this = self.project();
let _: Pin<&mut T> = this.pinned; // Pinned reference to the field
let _: &mut U = this.unpinned; // Normal reference to the field
}
}
```
[*code like this will be generated*][struct-default-expanded]
To use `#[pin_project]` on enums, you need to name the projection type
returned from the method.
```rust
use pin_project::pin_project;
use std::pin::Pin;
#[pin_project(project = EnumProj)]
enum Enum<T, U> {
Pinned(#[pin] T),
Unpinned(U),
}
impl<T, U> Enum<T, U> {
fn method(self: Pin<&mut Self>) {
match self.project() {
EnumProj::Pinned(x) => {
let _: Pin<&mut T> = x;
}
EnumProj::Unpinned(y) => {
let _: &mut U = y;
}
}
}
}
```
[*code like this will be generated*][enum-default-expanded]
See [documentation](https://docs.rs/pin-project) for more details, and
see [examples] directory for more examples and generated code.
## Related Projects
- [pin-project-lite]: A lightweight version of pin-project written with declarative macros.
[`pin_project`]: https://docs.rs/pin-project/1/pin_project/attr.pin_project.html
[enum-default-expanded]: examples/enum-default-expanded.rs
[examples]: examples/README.md
[pin-project-lite]: https://github.com/taiki-e/pin-project-lite
[pin-projection]: https://doc.rust-lang.org/std/pin/index.html#projections-and-structural-pinning
[struct-default-expanded]: examples/struct-default-expanded.rs
## License
Licensed under either of [Apache License, Version 2.0](LICENSE-APACHE) or
[MIT license](LICENSE-MIT) at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall
be dual licensed as above, without any additional terms or conditions.
|
