Name Description Size
lib.rs ! <!-- tidy:crate-doc:start --> A lightweight version of [pin-project] written with declarative macros. ## Usage Add this to your `Cargo.toml`: ```toml [dependencies] pin-project-lite = "0.2" ``` Compiler support: requires rustc 1.37+* ## Examples [`pin_project!`] macro creates a projection type covering all the fields of struct. ```rust use std::pin::Pin; use pin_project_lite::pin_project; 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 } } ``` To use [`pin_project!`] on enums, you need to name the projection type returned from the method. ```rust use std::pin::Pin; use pin_project_lite::pin_project; pin_project! { #[project = EnumProj] enum Enum<T, U> { Variant { #[pin] pinned: T, unpinned: U }, } } impl<T, U> Enum<T, U> { fn method(self: Pin<&mut Self>) { match self.project() { EnumProj::Variant { pinned, unpinned } => { let _: Pin<&mut T> = pinned; let _: &mut U = unpinned; } } } } ``` ## [pin-project] vs pin-project-lite Here are some similarities and differences compared to [pin-project]. ### Similar: Safety pin-project-lite guarantees safety in much the same way as [pin-project]. Both are completely safe unless you write other unsafe code. ### Different: Minimal design This library does not tackle as expansive of a range of use cases as [pin-project] does. If your use case is not already covered, please use [pin-project]. ### Different: No proc-macro related dependencies This is the **only** reason to use this crate. However, **if you already have proc-macro related dependencies in your crate's dependency graph, there is no benefit from using this crate.** (Note: There is almost no difference in the amount of code generated between [pin-project] and pin-project-lite.) ### Different: No useful error messages This macro does not handle any invalid input. So error messages are not to be useful in most cases. If you do need useful error messages, then upon error you can pass the same input to [pin-project] to receive a helpful description of the compile error. ### Different: No support for custom Unpin implementation pin-project supports this by [`UnsafeUnpin`][unsafe-unpin]. (`!Unpin` is supported by both [pin-project][not-unpin] and [pin-project-lite][not-unpin-lite].) ### Different: No support for tuple structs and tuple variants pin-project supports this. [not-unpin]: https://docs.rs/pin-project/1/pin_project/attr.pin_project.html#unpin [not-unpin-lite]: https://docs.rs/pin-project-lite/0.2/pin_project_lite/macro.pin_project.html#unpin [pin-project]: https://github.com/taiki-e/pin-project [unsafe-unpin]: https://docs.rs/pin-project/1/pin_project/attr.pin_project.html#unsafeunpin <!-- tidy:crate-doc:end --> 55384