├── .gitignore ├── Cargo.toml ├── .travis.yml ├── LICENSE-MIT ├── README.md ├── src └── lib.rs └── LICENSE-APACHE /.gitignore: -------------------------------------------------------------------------------- 1 | .DS_Store 2 | *~ 3 | *# 4 | *.o 5 | *.so 6 | *.swp 7 | *.dylib 8 | *.dSYM 9 | *.dll 10 | *.rlib 11 | *.dummy 12 | *.exe 13 | *-test 14 | /doc/ 15 | /target/ 16 | /examples/* 17 | !/examples/*.rs 18 | Cargo.lock 19 | 20 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | 3 | name = "void" 4 | version = "1.0.2" 5 | authors = ["Jonathan Reem "] 6 | repository = "https://github.com/reem/rust-void.git" 7 | description = "The uninhabited void type for use in statically impossible cases." 8 | readme = "README.md" 9 | license = "MIT / Apache-2.0" 10 | 11 | [features] 12 | 13 | default = ["std"] 14 | std = [] 15 | 16 | -------------------------------------------------------------------------------- /.travis.yml: -------------------------------------------------------------------------------- 1 | language: rust 2 | sudo: false 3 | 4 | rust: 5 | - 1.0.0 6 | - stable 7 | - beta 8 | - nightly 9 | 10 | script: 11 | - cargo build 12 | - cargo test 13 | - if [ "$TRAVIS_RUST_VERSION" != "1.0.0" ]; then cargo test --no-default-features; fi 14 | - cargo bench --no-run 15 | - cargo doc 16 | 17 | after_success: 18 | - if [ "$TRAVIS_PULL_REQUEST" == false && test == "TRAVIS_BRANCH" == "master" ]; then 19 | - curl https://raw.githubusercontent.com/reem/rust-gh-docs/master/make-docs.sh > docs.sh 20 | - chmod u+x docs.sh 21 | - ./docs.sh reem project-name 22 | 23 | env: 24 | global: 25 | secure: QPYL1XUr4CyK/2DXlsYC1eCpWRpyEiqQSd/FFVR+YdP/rOJ7AyAXQqPhfgjDBQwvc6E2fUiyYjoV/xe1a757DDeZKlgd8Lp20fSDwvNt/Ejx8ueh3h3kuOtgDpIGSKX/l+XC+ltDpzjhh7bowI2/fOEf+kE53jvu9i4PiLnKdlY= 26 | 27 | -------------------------------------------------------------------------------- /LICENSE-MIT: -------------------------------------------------------------------------------- 1 | Copyright (c) 2015 The rust-void Developers 2 | 3 | Permission is hereby granted, free of charge, to any person obtaining a copy 4 | of this software and associated documentation files (the "Software"), to deal 5 | in the Software without restriction, including without limitation the rights 6 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 7 | copies of the Software, and to permit persons to whom the Software is 8 | furnished to do so, subject to the following conditions: 9 | 10 | The above copyright notice and this permission notice shall be included in all 11 | copies or substantial portions of the Software. 12 | 13 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 14 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 15 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 16 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 17 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 18 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 19 | SOFTWARE. 20 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Void 2 | 3 | > The uninhabited void type for use in statically impossible cases. 4 | 5 | ## [Documentation](https://crates.fyi/crates/void/1.0.1) 6 | 7 | The uninhabited type, `enum Void { }` is useful in dealing with cases you 8 | know to be impossible. For instance, if you are implementing a trait which 9 | allows for error checking, but your case always succeeds, you can mark the 10 | error case or type as `Void`, signaling to the compiler it can never happen. 11 | 12 | This crate also comes packed with a few traits offering extension methods to 13 | `Result` and `Result`. 14 | 15 | ## Usage 16 | 17 | Use the crates.io repository; add this to your `Cargo.toml` along 18 | with the rest of your dependencies: 19 | 20 | ```toml 21 | [dependencies] 22 | void = "1" 23 | ``` 24 | 25 | Then, use `Void` in your crate: 26 | 27 | ```rust 28 | extern crate void; 29 | use void::Void; 30 | ``` 31 | 32 | ## Author 33 | 34 | [Jonathan Reem](https://medium.com/@jreem) is the primary author and maintainer of void. 35 | 36 | ## License 37 | 38 | Licensed under either of 39 | 40 | * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0) 41 | * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT) 42 | 43 | at your option. 44 | 45 | ### Contribution 46 | 47 | Unless you explicitly state otherwise, any contribution intentionally 48 | submitted for inclusion in the work by you, as defined in the Apache-2.0 49 | license, shall be dual licensed as above, without any additional terms or 50 | conditions. 51 | 52 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | #![cfg_attr(test, deny(warnings))] 2 | #![deny(missing_docs)] 3 | #![cfg_attr(not(feature = "std"), no_std)] 4 | 5 | //! # Void 6 | //! 7 | //! The uninhabited void type for use in statically impossible cases. 8 | //! 9 | //! In its own crate so all the users in the ecosystem can share the same type. 10 | //! This crate also comes ready with several extension traits for Result that add 11 | //! extra functionality to `Result` and `Result`. 12 | //! 13 | 14 | #[cfg(not(feature = "std"))] 15 | mod coreprovider { 16 | extern crate core; 17 | pub use core::{fmt, cmp}; 18 | } 19 | 20 | #[cfg(feature = "std")] 21 | mod coreprovider { 22 | pub use std::{fmt, cmp, error}; 23 | } 24 | 25 | use coreprovider::*; 26 | 27 | /// The empty type for cases which can't occur. 28 | #[derive(Copy)] 29 | pub enum Void { } 30 | 31 | impl Clone for Void { 32 | fn clone(&self) -> Void { 33 | unreachable(*self) 34 | } 35 | } 36 | 37 | impl fmt::Debug for Void { 38 | fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result { 39 | unreachable(*self) 40 | } 41 | } 42 | 43 | impl fmt::Display for Void { 44 | fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result { 45 | unreachable(*self) 46 | } 47 | } 48 | 49 | impl cmp::PartialEq for Void { 50 | fn eq(&self, _: &T) -> bool { 51 | unreachable(*self) 52 | } 53 | } 54 | 55 | impl cmp::PartialOrd for Void { 56 | fn partial_cmp(&self, _: &T) -> Option { 57 | unreachable(*self) 58 | } 59 | } 60 | 61 | #[cfg(feature = "std")] 62 | impl error::Error for Void { 63 | fn description(&self) -> &str { 64 | unreachable(*self) 65 | } 66 | 67 | fn cause(&self) -> Option<&error::Error> { 68 | unreachable(*self) 69 | } 70 | } 71 | 72 | /// A safe version of `intrinsincs::unreachable`. 73 | /// 74 | /// If this typechecks, anything that causes this to run is unreachable code. 75 | /// 76 | /// Calling this function in reachable code invokes undefined behavior, but 77 | /// should not be possible unless `unsafe` was used elsewhere to construct 78 | /// an instance of `Void` (which is already undefined behavior). 79 | #[inline(always)] 80 | pub fn unreachable(x: Void) -> ! { 81 | match x {} 82 | } 83 | 84 | /// Extensions to `Result` 85 | pub trait ResultVoidExt: Sized { 86 | /// Get the value out of a wrapper. 87 | fn void_unwrap(self) -> T; 88 | } 89 | 90 | impl ResultVoidExt for Result { 91 | /// Get the value out of an always-ok Result. 92 | /// 93 | /// Never panics, since it is statically known to be Ok. 94 | #[inline] 95 | fn void_unwrap(self) -> T { 96 | match self { 97 | Ok(val) => val, 98 | Err(e) => unreachable(e) 99 | } 100 | } 101 | } 102 | 103 | /// Extensions to `Result` 104 | pub trait ResultVoidErrExt: Sized { 105 | /// Get the error out of a wrapper. 106 | fn void_unwrap_err(self) -> E; 107 | } 108 | 109 | impl ResultVoidErrExt for Result { 110 | /// Get the error out of an always-err Result. 111 | /// 112 | /// Never panics, since it is statically known to be Err. 113 | #[inline] 114 | fn void_unwrap_err(self) -> E { 115 | match self { 116 | Ok(v) => unreachable(v), 117 | Err(e) => e 118 | } 119 | } 120 | } 121 | 122 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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