1[](https://github.com/nvzqz/static-assertions-rs) 2 3<div align="center"> 4 <a href="https://crates.io/crates/static_assertions"> 5 <img src="https://img.shields.io/crates/v/static_assertions.svg" alt="Crates.io"> 6 <img src="https://img.shields.io/crates/d/static_assertions.svg" alt="Downloads"> 7 </a> 8 <a href="https://travis-ci.org/nvzqz/static-assertions-rs"> 9 <img src="https://travis-ci.org/nvzqz/static-assertions-rs.svg?branch=master" alt="Build Status"> 10 </a> 11 <img src="https://img.shields.io/badge/rustc-^1.37.0-blue.svg" alt="rustc ^1.37.0"> 12 <br> 13 <a href="https://www.patreon.com/nvzqz"> 14 <img src="https://c5.patreon.com/external/logo/become_a_patron_button.png" alt="Become a Patron!" height="35"> 15 </a> 16 <a href="https://www.paypal.me/nvzqz"> 17 <img src="https://buymecoffee.intm.org/img/button-paypal-white.png" alt="Buy me a coffee" height="35"> 18 </a> 19</div> 20 21Compile-time assertions for Rust, brought to you by 22[Nikolai Vazquez](https://twitter.com/NikolaiVazquez). 23 24This library lets you ensure correct assumptions about constants, types, and 25more. See the [docs] and [FAQ](#faq) for more info! 26 27## Installation 28 29This crate is available 30[on crates.io](https://crates.io/crates/static_assertions) and can be used by 31adding the following to your project's 32[`Cargo.toml`](https://doc.rust-lang.org/cargo/reference/manifest.html): 33 34```toml 35[dependencies] 36static_assertions = "1.1.0" 37``` 38 39and this to your crate root (`main.rs` or `lib.rs`): 40 41```rust 42#[macro_use] 43extern crate static_assertions; 44``` 45 46## Usage 47 48This crate exposes the following macros: 49- [`assert_cfg!`] 50- [`assert_eq_align!`] 51- [`assert_eq_size!`] 52- [`assert_eq_size_ptr!`] 53- [`assert_eq_size_val!`] 54- [`assert_fields!`] 55- [`assert_impl_all!`] 56- [`assert_impl_any!`] 57- [`assert_impl_one!`] 58- [`assert_not_impl_all!`] 59- [`assert_not_impl_any!`] 60- [`assert_obj_safe!`] 61- [`assert_trait_sub_all!`] 62- [`assert_trait_super_all!`] 63- [`assert_type_eq_all!`] 64- [`assert_type_ne_all!`] 65- [`const_assert!`] 66- [`const_assert_eq!`] 67- [`const_assert_ne!`] 68 69## FAQ 70 71- **Q:** When would I want to use this? 72 73 **A:** This library is useful for when wanting to ensure properties of 74 constants, types, and traits. 75 76 Basic examples: 77 78 - With the release of 1.39, `str::len` can be called in a `const` 79 context. Using [`const_assert!`], one can check that a string generated from 80 elsewhere is of a given size: 81 82 ```rust 83 const DATA: &str = include_str!("path/to/string.txt"); 84 85 const_assert!(DATA.len() < 512); 86 ``` 87 88 - Have a type that absolutely must implement certain traits? With 89 [`assert_impl_all!`], one can ensure this: 90 91 ```rust 92 struct Foo { 93 value: // ... 94 } 95 96 assert_impl_all!(Foo: Send, Sync); 97 ``` 98 99- **Q:** How can I contribute? 100 101 **A:** A couple of ways! You can: 102 103 - Attempt coming up with some form of static analysis that you'd like to see 104 implemented. Create a [new issue] and describe how you'd imagine your 105 assertion to work, with example code to demonstrate. 106 107 - Implement your own static assertion and create a [pull request]. 108 109 - Give feedback. What are some pain points? Where is it unpleasant? 110 111 - Write docs. If you're familiar with how this library works, sharing your 112 knowledge with the rest its users would be great! 113 114- **Q:** Will this affect my compiled binary? 115 116 **A:** Nope! There is zero runtime cost to using this because all checks are 117 at compile-time, and so no code is emitted to run. 118 119- **Q:** Will this affect my compile times? 120 121 **A:** Likely not by anything perceivable. If this is a concern, this library 122 can be put in `dev-dependencies`: 123 124 ```toml 125 [dev-dependencies] 126 static_assertions = "1.1.0" 127 ``` 128 129 and then assertions can be conditionally run behind `#[cfg(test)]`: 130 131 ```rust 132 #[cfg(test)] 133 const_assert_eq!(MEANING_OF_LIFE, 42); 134 ``` 135 136 However, the assertions will only be checked when running `cargo test`. This 137 somewhat defeats the purpose of catching false static conditions up-front with 138 a compilation failure. 139 140- **Q:** What is `const _`? 141 142 **A:** It's a way of creating an unnamed constant. This is used so that macros 143 can be called from a global scope without requiring a scope-unique label. This 144 library makes use of the side effects of evaluating the `const` expression. 145 See the feature's 146 [tracking issue](https://github.com/rust-lang/rust/issues/54912) 147 and 148 [issue #1](https://github.com/nvzqz/static-assertions-rs/issues/1) 149 for more info. 150 151## Changes 152 153See [`CHANGELOG.md`](https://github.com/nvzqz/static-assertions-rs/blob/master/CHANGELOG.md) 154for a complete list of what has changed from one version to another. 155 156## License 157 158This project is released under either: 159 160- [MIT License](https://github.com/nvzqz/static-assertions-rs/blob/master/LICENSE-MIT) 161 162- [Apache License (Version 2.0)](https://github.com/nvzqz/static-assertions-rs/blob/master/LICENSE-APACHE) 163 164at your choosing. 165 166[new issue]: https://github.com/nvzqz/static-assertions-rs/issues/new 167[pull request]: https://github.com/nvzqz/static-assertions-rs/pulls 168[docs]: https://docs.rs/static_assertions 169 170[`assert_cfg!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_cfg.html 171[`assert_eq_align!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_eq_align.html 172[`assert_eq_size!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_eq_size.html 173[`assert_eq_size_ptr!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_eq_size_ptr.html 174[`assert_eq_size_val!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_eq_size_val.html 175[`assert_fields!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_fields.html 176[`assert_impl_all!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_impl_all.html 177[`assert_impl_any!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_impl_any.html 178[`assert_impl_one!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_impl_one.html 179[`assert_not_impl_all!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_not_impl_all.html 180[`assert_not_impl_any!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_not_impl_any.html 181[`assert_obj_safe!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_obj_safe.html 182[`assert_trait_sub_all!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_trait_sub_all.html 183[`assert_trait_super_all!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_trait_super_all.html 184[`assert_type_eq_all!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_type_eq_all.html 185[`assert_type_ne_all!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.assert_type_ne_all.html 186[`const_assert!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.const_assert.html 187[`const_assert_eq!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.const_assert_eq.html 188[`const_assert_ne!`]: https://docs.rs/static_assertions/1.1.0/static_assertions/macro.const_assert_ne.html 189
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