Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 186 insertions, 0 deletions

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+[<img alt="github" src="https://img.shields.io/badge/github-self__cell-8da0cb?style=for-the-badge&logo=github" height="20">](https://github.com/Voultapher/self_cell)
+[<img alt="crates.io" src="https://img.shields.io/badge/dynamic/json?color=fc8d62&label=crates.io&query=%24.crate.max_version&url=https%3A%2F%2Fcrates.io%2Fapi%2Fv1%2Fcrates%2Fself_cell&style=for-the-badge&logo=rust" height="20">](https://crates.io/crates/self_cell)
+[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-self__cell-66c2a5?style=for-the-badge&logoColor=white&logo=data:image/svg+xml;base64,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" height="20">](https://docs.rs/self_cell)
+
+# `self_cell!`
+
+Use the macro-rules macro: `self_cell!` to create safe-to-use self-referential
+structs in stable Rust, without leaking the struct internal lifetime.
+
+In a nutshell, the API looks *roughly* like this:
+
+```rust
+// User code:
+
+self_cell!(
+    struct NewStructName {
+        owner: Owner,
+
+        #[covariant]
+        dependent: Dependent,
+    }
+    
+    impl {Debug}
+);
+
+// Generated by macro:
+
+struct NewStructName(...);
+
+impl NewStructName {
+    fn new(
+        owner: Owner,
+        dependent_builder: impl for<'a> FnOnce(&'a Owner) -> Dependent<'a>
+    ) -> NewStructName { ... }
+    fn borrow_owner<'a>(&'a self) -> &'a Owner { ... }
+    fn borrow_dependent<'a>(&'a self) -> &'a Dependent<'a> { ... }
+}
+
+impl Debug for NewStructName { ... }
+```
+
+Self-referential structs are currently not supported with safe vanilla Rust. The
+only reasonable safe alternative is to expect the user to juggle 2 separate data
+structures which is a mess. The library solution ouroboros is really expensive
+to compile due to its use of procedural macros.
+
+This alternative is `no_std`, uses no proc-macros, some self contained unsafe
+and works on stable Rust, and is miri tested. With a total of less than 300
+lines of implementation code, which consists mostly of type and trait
+implementations, this crate aims to be a good minimal solution to the problem of
+self-referential structs.
+
+It has undergone [community code review](https://users.rust-lang.org/t/experimental-safe-to-use-proc-macro-free-self-referential-structs-in-stable-rust/52775)
+from experienced Rust users.
+
+### Fast compile times
+
+```
+$ rm -rf target && cargo +nightly build -Z timings
+
+Compiling self_cell v0.9.0
+Completed self_cell v0.9.0 in 0.2s
+```
+
+Because it does **not** use proc-macros, and has 0 dependencies compile-times
+are fast.
+
+Measurements done on a slow laptop.
+
+### A motivating use case
+
+```rust
+use self_cell::self_cell;
+
+#[derive(Debug, Eq, PartialEq)]
+struct Ast<'a>(pub Vec<&'a str>);
+
+self_cell!(
+    struct AstCell {
+        owner: String,
+
+        #[covariant]
+        dependent: Ast,
+    }
+
+    impl {Debug, Eq, PartialEq}
+);
+
+fn build_ast_cell(code: &str) -> AstCell {
+    // Create owning String on stack.
+    let pre_processed_code = code.trim().to_string();
+
+    // Move String into AstCell, then build Ast inplace.
+    AstCell::new(
+        pre_processed_code,
+        |code| Ast(code.split(' ').filter(|word| word.len() > 1).collect())
+    )
+}
+
+fn main() {
+    let ast_cell = build_ast_cell("fox = cat + dog");
+
+    println!("ast_cell -> {:?}", &ast_cell);
+    println!("ast_cell.borrow_owner() -> {:?}", ast_cell.borrow_owner());
+    println!("ast_cell.borrow_dependent().0[1] -> {:?}", ast_cell.borrow_dependent().0[1]);
+}
+```
+
+```
+$ cargo run
+
+ast_cell -> AstCell { owner: "fox = cat + dog", dependent: Ast(["fox", "cat", "dog"]) }
+ast_cell.borrow_owner() -> "fox = cat + dog"
+ast_cell.borrow_dependent().0[1] -> "cat"
+```
+
+There is no way in safe Rust to have an API like `build_ast_cell`, as soon as
+`Ast` depends on stack variables like `pre_processed_code` you can't return the
+value out of the function anymore. You could move the pre-processing into the
+caller but that gets ugly quickly because you can't encapsulate things anymore.
+Note this is a somewhat niche use case, self-referential structs should only be
+used when there is no good alternative.
+
+Under the hood, it heap allocates a struct which it initializes first by moving
+the owner value to it and then using the reference to this now Pin/Immovable
+owner to construct the dependent inplace next to it. This makes it safe to move
+the generated SelfCell but you have to pay for the heap allocation.
+
+See the documentation for a more in-depth API overview and advanced examples:
+https://docs.rs/self_cell
+
+### Installing
+
+[See cargo docs](https://doc.rust-lang.org/cargo/guide/).
+
+## Running the tests
+
+```
+cargo test
+
+cargo miri test
+```
+
+### Related projects
+
+[ouroboros](https://github.com/joshua-maros/ouroboros)
+
+[rental](https://github.com/jpernst/rental)
+
+[Schroedinger](https://github.com/dureuill/sc)
+
+[owning_ref](https://github.com/Kimundi/owning-ref-rs)
+
+[ghost-cell](https://github.com/matthieu-m/ghost-cell)
+
+## Min required rustc version
+
+By default the minimum required rustc version is 1.51.
+
+There is an optional feature you can enable called "old_rust" that enables
+support down to rustc version 1.36. However this requires polyfilling std
+library functionality for older rustc with technically UB versions. Testing does
+not show older rustc versions (ab)using this. Use at your own risk.
+
+The minimum versions are a best effor and may change with any new major release.
+
+## Contributing
+
+Please respect the [CODE_OF_CONDUCT.md](CODE_OF_CONDUCT.md) when contributing.
+
+## Versioning
+
+We use [SemVer](http://semver.org/) for versioning. For the versions available,
+see the [tags on this repository](https://github.com/Voultapher/self_cell/tags).
+
+## Authors
+
+* **Lukas Bergdoll** - *Initial work* - [Voultapher](https://github.com/Voultapher)
+
+See also the list of [contributors](https://github.com/Voultapher/self_cell/contributors)
+who participated in this project.
+
+## License
+
+This project is licensed under the Apache License, Version 2.0 -
+see the [LICENSE.md](LICENSE.md) file for details.