├── .gitignore ├── .travis.yml ├── CHANGELOG.md ├── COPYRIGHT ├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── README.md ├── examples ├── no_std.rs ├── no_std_or_alloc.rs └── simple.rs └── src └── lib.rs /.gitignore: -------------------------------------------------------------------------------- 1 | /target/ 2 | /Cargo.lock 3 | -------------------------------------------------------------------------------- /.travis.yml: -------------------------------------------------------------------------------- 1 | language: rust 2 | rust: 3 | - nightly 4 | - beta 5 | - stable 6 | #env: 7 | # global: 8 | # - secure: TODO 9 | script: 10 | - if [[ "$(rustc --version)" =~ -(dev|nightly) ]]; then cargo test --features no_std_examples; else ! cargo test --features no_std_examples; fi 11 | - cargo test 12 | # - cargo doc 13 | #after_script: 14 | # - ln -s target/doc doc 15 | # - curl http://www.rust-ci.org/artifacts/put?t=$RUSTCI_TOKEN | sh 16 | -------------------------------------------------------------------------------- /CHANGELOG.md: -------------------------------------------------------------------------------- 1 | Unreleased (2016-06-03) 2 | ======================= 3 | 4 | Plenty of breaking changes. 5 | 6 | - The `no_std` Cargo feature was removed; `#[no_std]` has stabilised in Rust, 7 | and so the `mopa` crate is now *always* `#[no_std]`. 8 | Note that the `no_std_examples` Cargo feature is still around, because of 9 | shortcomings in Cargo itself. It’s not intended for client use, though; only 10 | for being able to run the `no_std` and `no_std_or_alloc` examples from this 11 | repository. 12 | 13 | - `mopa` trait no longer needs the `no_std` feature in order not to depend on 14 | 15 | - `mopafy!` syntax changed for advanced cases, simplifying things a little. 16 | 17 | - `mopafy!(Trait)` is unchanged. 18 | 19 | - `mopafy!(Trait, core = name_of_libcore_crate)` → `mopafy!(Trait, only core)`. 20 | (That’s the literal token `core`, not the name of the libcore crate.) 21 | 22 | - `mopafy!(Trait, core = name_of_libcore_crate, alloc = name_of_liballoc_crate)` → 23 | `use alloc::boxed::Box; mopafy!(Trait);` 24 | 25 | 0.2.2 (2016-04-05) 26 | ================== 27 | 28 | - Dead code warnings suppressed. 29 | 30 | 0.2.1 (2016-01-22) 31 | ================== 32 | 33 | - Update for Rust `#[no_std]` compatibility. 34 | 35 | 0.2.0 (2015-05-13) 36 | ================== 37 | 38 | - Support beta/stable. 39 | 40 | - Traits being mopafied now need to extend `mopa::Any`, not `std::any::Any`. 41 | This is a breaking change. 42 | 43 | - Users of `#[no_std]` will now need to enable the `no_std` Cargo feature on 44 | this crate. 45 | 46 | - `#![feature(core)]` is no longer necessary. 47 | 48 | 0.1.1–0.1.8 (2015-01-07–2015-04-14) 49 | =================================== 50 | 51 | Updates to cope with Rust language changes. 52 | This is ancient history, before Rust 1.0.0. 53 | 54 | 0.1.0 (2015-01-06) 55 | ================== 56 | 57 | Initial release. Supports nightly channel only. 58 | (OK, so at this point there *was* only nightly.) 59 | -------------------------------------------------------------------------------- /COPYRIGHT: -------------------------------------------------------------------------------- 1 | This project is dual-licensed under the terms of the MIT and Apache (version 2.0) licenses. 2 | 3 | Copyright (c) 2014 Chris Morgan and The Rust Project Developers 4 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "mopa" 3 | version = "0.2.2" 4 | authors = ["Chris Morgan "] 5 | description = "My Own Personal Any: get your own Any with additional functionality" 6 | #documentation = 7 | #homepage = 8 | repository = "https://github.com/chris-morgan/mopa" 9 | readme = "README.md" 10 | keywords = ["any", "macro"] 11 | license = "MIT/Apache-2.0" 12 | 13 | [features] 14 | no_std_examples = [] 15 | -------------------------------------------------------------------------------- /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. Definitions. 8 | 9 | "License" shall mean the terms and conditions for use, reproduction, 10 | and distribution as defined by Sections 1 through 9 of this document. 11 | 12 | "Licensor" shall mean the copyright owner or entity authorized by 13 | the copyright owner that is granting the License. 14 | 15 | "Legal Entity" shall mean the union of the acting entity and all 16 | other entities that control, are controlled by, or are under common 17 | control with that entity. For the purposes of this definition, 18 | "control" means (i) the power, direct or indirect, to cause the 19 | direction or management of such entity, whether by contract or 20 | otherwise, or (ii) ownership of fifty percent (50%) or more of the 21 | outstanding shares, or (iii) beneficial ownership of such entity. 22 | 23 | "You" (or "Your") shall mean an individual or Legal Entity 24 | exercising permissions granted by this License. 25 | 26 | "Source" form shall mean the preferred form for making modifications, 27 | including but not limited to software source code, documentation 28 | source, and configuration files. 29 | 30 | "Object" form shall mean any form resulting from mechanical 31 | transformation or translation of a Source form, including but 32 | not limited to compiled object code, generated documentation, 33 | and conversions to other media types. 34 | 35 | "Work" shall mean the work of authorship, whether in Source or 36 | Object form, made available under the License, as indicated by a 37 | copyright notice that is included in or attached to the work 38 | (an example is provided in the Appendix below). 39 | 40 | "Derivative Works" shall mean any work, whether in Source or Object 41 | form, that is based on (or derived from) the Work and for which the 42 | editorial revisions, annotations, elaborations, or other modifications 43 | represent, as a whole, an original work of authorship. For the purposes 44 | of this License, Derivative Works shall not include works that remain 45 | separable from, or merely link (or bind by name) to the interfaces of, 46 | the Work and Derivative Works thereof. 47 | 48 | "Contribution" shall mean any work of authorship, including 49 | the original version of the Work and any modifications or additions 50 | to that Work or Derivative Works thereof, that is intentionally 51 | submitted to Licensor for inclusion in the Work by the copyright owner 52 | or by an individual or Legal Entity authorized to submit on behalf of 53 | the copyright owner. For the purposes of this definition, "submitted" 54 | means any form of electronic, verbal, or written communication sent 55 | to the Licensor or its representatives, including but not limited to 56 | communication on electronic mailing lists, source code control systems, 57 | and issue tracking systems that are managed by, or on behalf of, the 58 | Licensor for the purpose of discussing and improving the Work, but 59 | excluding communication that is conspicuously marked or otherwise 60 | designated in writing by the copyright owner as "Not a Contribution." 61 | 62 | "Contributor" shall mean Licensor and any individual or Legal Entity 63 | on behalf of whom a Contribution has been received by Licensor and 64 | subsequently incorporated within the Work. 65 | 66 | 2. Grant of Copyright License. Subject to the terms and conditions of 67 | this License, each Contributor hereby grants to You a perpetual, 68 | worldwide, non-exclusive, no-charge, royalty-free, irrevocable 69 | copyright license to reproduce, prepare Derivative Works of, 70 | publicly display, publicly perform, sublicense, and distribute the 71 | Work and such Derivative Works in Source or Object form. 72 | 73 | 3. Grant of Patent License. Subject to the terms and conditions of 74 | this License, each Contributor hereby grants to You a perpetual, 75 | worldwide, non-exclusive, no-charge, royalty-free, irrevocable 76 | (except as stated in this section) patent license to make, have made, 77 | use, offer to sell, sell, import, and otherwise transfer the Work, 78 | where such license applies only to those patent claims licensable 79 | by such Contributor that are necessarily infringed by their 80 | Contribution(s) alone or by combination of their Contribution(s) 81 | with the Work to which such Contribution(s) was submitted. If You 82 | institute patent litigation against any entity (including a 83 | cross-claim or counterclaim in a lawsuit) alleging that the Work 84 | or a Contribution incorporated within the Work constitutes direct 85 | or contributory patent infringement, then any patent licenses 86 | granted to You under this License for that Work shall terminate 87 | as of the date such litigation is filed. 88 | 89 | 4. Redistribution. You may reproduce and distribute copies of the 90 | Work or Derivative Works thereof in any medium, with or without 91 | modifications, and in Source or Object form, provided that You 92 | meet the following conditions: 93 | 94 | (a) You must give any other recipients of the Work or 95 | Derivative Works a copy of this License; and 96 | 97 | (b) You must cause any modified files to carry prominent notices 98 | stating that You changed the files; and 99 | 100 | (c) You must retain, in the Source form of any Derivative Works 101 | that You distribute, all copyright, patent, trademark, and 102 | attribution notices from the Source form of the Work, 103 | excluding those notices that do not pertain to any part of 104 | the Derivative Works; and 105 | 106 | (d) If the Work includes a "NOTICE" text file as part of its 107 | distribution, then any Derivative Works that You distribute must 108 | include a readable copy of the attribution notices contained 109 | within such NOTICE file, excluding those notices that do not 110 | pertain to any part of the Derivative Works, in at least one 111 | of the following places: within a NOTICE text file distributed 112 | as part of the Derivative Works; within the Source form or 113 | documentation, if provided along with the Derivative Works; or, 114 | within a display generated by the Derivative Works, if and 115 | wherever such third-party notices normally appear. The contents 116 | of the NOTICE file are for informational purposes only and 117 | do not modify the License. You may add Your own attribution 118 | notices within Derivative Works that You distribute, alongside 119 | or as an addendum to the NOTICE text from the Work, provided 120 | that such additional attribution notices cannot be construed 121 | as modifying the License. 122 | 123 | You may add Your own copyright statement to Your modifications and 124 | may provide additional or different license terms and conditions 125 | for use, reproduction, or distribution of Your modifications, or 126 | for any such Derivative Works as a whole, provided Your use, 127 | reproduction, and distribution of the Work otherwise complies with 128 | the conditions stated in this License. 129 | 130 | 5. Submission of Contributions. Unless You explicitly state otherwise, 131 | any Contribution intentionally submitted for inclusion in the Work 132 | by You to the Licensor shall be under the terms and conditions of 133 | this License, without any additional terms or conditions. 134 | Notwithstanding the above, nothing herein shall supersede or modify 135 | the terms of any separate license agreement you may have executed 136 | with Licensor regarding such Contributions. 137 | 138 | 6. Trademarks. This License does not grant permission to use the trade 139 | names, trademarks, service marks, or product names of the Licensor, 140 | except as required for reasonable and customary use in describing the 141 | origin of the Work and reproducing the content of the NOTICE file. 142 | 143 | 7. Disclaimer of Warranty. Unless required by applicable law or 144 | agreed to in writing, Licensor provides the Work (and each 145 | Contributor provides its Contributions) on an "AS IS" BASIS, 146 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 147 | implied, including, without limitation, any warranties or conditions 148 | of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A 149 | PARTICULAR PURPOSE. You are solely responsible for determining the 150 | appropriateness of using or redistributing the Work and assume any 151 | risks associated with Your exercise of permissions under this License. 152 | 153 | 8. Limitation of Liability. In no event and under no legal theory, 154 | whether in tort (including negligence), contract, or otherwise, 155 | unless required by applicable law (such as deliberate and grossly 156 | negligent acts) or agreed to in writing, shall any Contributor be 157 | liable to You for damages, including any direct, indirect, special, 158 | incidental, or consequential damages of any character arising as a 159 | result of this License or out of the use or inability to use the 160 | Work (including but not limited to damages for loss of goodwill, 161 | work stoppage, computer failure or malfunction, or any and all 162 | other commercial damages or losses), even if such Contributor 163 | has been advised of the possibility of such damages. 164 | 165 | 9. Accepting Warranty or Additional Liability. While redistributing 166 | the Work or Derivative Works thereof, You may choose to offer, 167 | and charge a fee for, acceptance of support, warranty, indemnity, 168 | or other liability obligations and/or rights consistent with this 169 | License. However, in accepting such obligations, You may act only 170 | on Your own behalf and on Your sole responsibility, not on behalf 171 | of any other Contributor, and only if You agree to indemnify, 172 | defend, and hold each Contributor harmless for any liability 173 | incurred by, or claims asserted against, such Contributor by reason 174 | of your accepting any such warranty or additional liability. 175 | 176 | END OF TERMS AND CONDITIONS 177 | 178 | APPENDIX: How to apply the Apache License to your work. 179 | 180 | To apply the Apache License to your work, attach the following 181 | boilerplate notice, with the fields enclosed by brackets "[]" 182 | replaced with your own identifying information. (Don't include 183 | the brackets!) The text should be enclosed in the appropriate 184 | comment syntax for the file format. We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright [yyyy] [name of copyright owner] 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /LICENSE-MIT: -------------------------------------------------------------------------------- 1 | Copyright (c) 2014 Chris Morgan and The Rust Project Developers 2 | 3 | Permission is hereby granted, free of charge, to any 4 | person obtaining a copy of this software and associated 5 | documentation files (the "Software"), to deal in the 6 | Software without restriction, including without 7 | limitation the rights to use, copy, modify, merge, 8 | publish, distribute, sublicense, and/or sell copies of 9 | the Software, and to permit persons to whom the Software 10 | is furnished to do so, subject to the following 11 | conditions: 12 | 13 | The above copyright notice and this permission notice 14 | shall be included in all copies or substantial portions 15 | of the Software. 16 | 17 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF 18 | ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED 19 | TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 20 | PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT 21 | SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 22 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 23 | OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR 24 | IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 25 | DEALINGS IN THE SOFTWARE. 26 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | MOPA: My Own Personal Any 2 | ========================= 3 | 4 | [![Build Status](https://travis-ci.org/chris-morgan/mopa.svg?branch=master)](https://travis-ci.org/chris-morgan/mopa) 5 | 6 | 7 | 8 | A macro to implement all the `Any` methods on your own trait. 9 | 10 | You like `Any`—its ability to store any `'static` type as a trait object and then downcast it 11 | back to the original type is very convenient, and in fact you need it for whatever misguided 12 | reason. But it’s not enough. What you *really* want is your own trait object type with `Any`’s 13 | functionality glued onto it. Maybe you have a `Person` trait and you want your people to be 14 | able to do various things, but you also want to be able to conveniently downcast the person to 15 | its original type, right? Alas, you can’t write a type like `Box` (at present, 16 | anyway). So what do you do instead? Do you give up? No, no! No, no! Enter MOPA. 17 | 18 | > There once was a quite friendly trait 19 | > Called `Person`, with much on its plate. 20 | >     “I need to be `Any` 21 | >     To downcast to `Benny`— 22 | > But I’m not, so I guess I’ll just wait.” 23 | 24 | A pitiful tale, isn’t it? Especially given that there was a bear chasing it with intent to eat 25 | it. Fortunately now you can *mopafy* `Person` in three simple steps: 26 | 27 | 1. Add the `mopa` crate to your `Cargo.toml` as usual and your crate root like so: 28 | 29 | ```rust 30 | #[macro_use] 31 | extern crate mopa; 32 | ``` 33 | 34 | 2. Make `Any` (`mopa::Any`, not `std::any::Any`) a supertrait of `Person`; 35 | 36 | 3. `mopafy!(Person);`. 37 | 38 | And lo, you can now write `person.is::()` and `person.downcast_ref::()` and so on 39 | to your heart’s content. Simple, huh? 40 | 41 | Oh, by the way, it was actually the person on the bear’s plate. There wasn’t really anything on 42 | `Person`’s plate after all. 43 | 44 | ```rust 45 | #[macro_use] 46 | extern crate mopa; 47 | 48 | struct Bear { 49 | // This might be a pretty fat bear. 50 | fatness: u16, 51 | } 52 | 53 | impl Bear { 54 | fn eat(&mut self, person: Box) { 55 | self.fatness = (self.fatness as i16 + person.weight()) as u16; 56 | } 57 | } 58 | 59 | trait Person: mopa::Any { 60 | fn panic(&self); 61 | fn yell(&self) { println!("Argh!"); } 62 | fn sleep(&self); 63 | fn weight(&self) -> i16; 64 | } 65 | 66 | mopafy!(Person); 67 | 68 | struct Benny { 69 | // (Benny is not a superhero. He can’t carry more than 256kg of food at once.) 70 | kilograms_of_food: u8, 71 | } 72 | 73 | impl Person for Benny { 74 | fn panic(&self) { self.yell() } 75 | fn sleep(&self) { /* ... */ } 76 | fn weight(&self) -> i16 { 77 | // Who’s trying to find out? I’m scared! 78 | self.yell(); 79 | self.kilograms_of_food as i16 + 60 80 | } 81 | } 82 | 83 | struct Chris; 84 | 85 | impl Chris { 86 | // Normal people wouldn’t be brave enough to hit a bear but Chris might. 87 | fn hit(&self, bear: &mut Bear) { 88 | println!("Chris hits the bear! How brave! (Or maybe stupid?)"); 89 | // Meh, boundary conditions, what use are they in examples? 90 | // Chris clearly hits quite hard. Poor bear. 91 | bear.fatness -= 1; 92 | } 93 | } 94 | 95 | impl Person for Chris { 96 | fn panic(&self) { /* ... */ } 97 | fn sleep(&self) { /* ... */ } 98 | fn weight(&self) -> i16 { -5 /* antigravity device! cool! */ } 99 | } 100 | 101 | fn simulate_simulation(person: Box, bear: &mut Bear) { 102 | if person.is::() { 103 | // None of the others do, but Benny knows this particular 104 | // bear by reputation and he’s *really* going to be worried. 105 | person.yell() 106 | } 107 | // If it happens to be Chris, he’ll hit the bear. 108 | person.downcast_ref::().map(|chris| chris.hit(bear)); 109 | bear.eat(person); 110 | } 111 | 112 | fn main() { 113 | let mut bear = Bear { fatness: 10 }; 114 | simulate_simulation(Box::new(Benny { kilograms_of_food: 5 }), &mut bear); 115 | simulate_simulation(Box::new(Chris), &mut bear); 116 | } 117 | ``` 118 | 119 | Now *should* you do something like this? Probably not. Enums are probably a better solution for 120 | this particular case as written; frankly I believe that almost the only time you should 121 | downcast an `Any` trait object (or a mopafied trait object) is with a generic parameter, when 122 | producing something like `AnyMap`, for example. If you control *all* the code, `Any` trait 123 | objects are probably not the right solution; they’re good for cases with user-defined 124 | types across a variety of libraries. But the question of purpose and suitability is open, and I 125 | don’t have a really good example of such a use case here at present. TODO. 126 | 127 | Usage 128 | ----- 129 | 130 | Cargo all the way. http://crates.io/crates/mopa 131 | 132 | Author 133 | ------ 134 | 135 | [Chris Morgan](https://chrismorgan.info/) ([chris-morgan](https://github.com/chris-morgan)) is the primary author and maintainer of this library. 136 | 137 | License 138 | ------- 139 | 140 | This library is distributed under similar terms to Rust: dual licensed under the MIT license and the Apache license (version 2.0). 141 | 142 | See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details. 143 | -------------------------------------------------------------------------------- /examples/no_std.rs: -------------------------------------------------------------------------------- 1 | // This example depends on the no_std_examples feature being enabled on the crate; 2 | // without it, we have to go and chop everything off so that it can compile. 3 | // If you are basing something off this example, please note that all the `feature = 4 | // "no_std_examples"` 5 | // cfg-gating is a workaround for Cargo until https://github.com/rust-lang/cargo/issues/1570 lands. 6 | // Do not include it if you copy any code. 7 | 8 | #![cfg_attr(feature = "no_std_examples", feature(lang_items, start, alloc))] 9 | #![cfg_attr(feature = "no_std_examples", no_std)] 10 | 11 | #[cfg(not(feature = "no_std_examples"))] 12 | fn main() { } 13 | 14 | #[cfg(feature = "no_std_examples")] 15 | #[macro_use] 16 | extern crate mopa; 17 | 18 | #[cfg(feature = "no_std_examples")] 19 | extern crate alloc; 20 | 21 | #[cfg(feature = "no_std_examples")] 22 | mod silly_wrapper_to_save_writing_the_whole_cfg_incantation_on_every_item { 23 | use alloc::boxed::Box; 24 | 25 | trait Panic { fn panic(&self) { } } 26 | 27 | trait PanicAny: Panic + ::mopa::Any { } 28 | 29 | mopafy!(PanicAny); 30 | 31 | impl Panic for i32 { } 32 | 33 | impl PanicAny for T { } 34 | 35 | #[start] 36 | fn start(_argc: isize, _argv: *const *const u8) -> isize { 37 | let p: &PanicAny = &2; 38 | if p.is::() { 39 | 0 40 | } else { 41 | 1 42 | } 43 | } 44 | 45 | #[lang = "eh_personality"] extern fn eh_personality() {} 46 | #[lang = "panic_fmt"] extern fn panic_fmt() {} 47 | } 48 | -------------------------------------------------------------------------------- /examples/no_std_or_alloc.rs: -------------------------------------------------------------------------------- 1 | // This example depends on the no_std_examples feature being enabled on the crate; 2 | // without it, we have to go and chop everything off so that it can compile. 3 | // If you are basing something off this example, please note that all the `feature = 4 | // "no_std_examples"` 5 | // cfg-gating is a workaround for Cargo until https://github.com/rust-lang/cargo/issues/1570 lands. 6 | // Do not include it if you copy any code. 7 | 8 | #![cfg_attr(feature = "no_std_examples", feature(lang_items, start, libc))] 9 | #![cfg_attr(feature = "no_std_examples", no_std)] 10 | 11 | #[cfg(not(feature = "no_std_examples"))] 12 | fn main() { } 13 | 14 | #[cfg(feature = "no_std_examples")] 15 | #[macro_use] 16 | extern crate mopa; 17 | 18 | #[cfg(feature = "no_std_examples")] 19 | extern crate libc; 20 | 21 | #[cfg(feature = "no_std_examples")] 22 | mod silly_wrapper_to_save_writing_the_whole_cfg_incantation_on_every_item { 23 | trait Panic { fn panic(&self) { } } 24 | 25 | trait PanicAny: Panic + ::mopa::Any { } 26 | 27 | mopafy!(PanicAny, only core); 28 | 29 | impl Panic for i32 { } 30 | 31 | impl PanicAny for T { } 32 | 33 | #[start] 34 | fn start(_argc: isize, _argv: *const *const u8) -> isize { 35 | let p: &PanicAny = &2; 36 | if p.is::() { 37 | 0 38 | } else { 39 | 1 40 | } 41 | } 42 | 43 | #[lang = "eh_personality"] extern fn eh_personality() {} 44 | #[lang = "panic_fmt"] extern fn panic_fmt() {} 45 | } 46 | -------------------------------------------------------------------------------- /examples/simple.rs: -------------------------------------------------------------------------------- 1 | #[macro_use] 2 | extern crate mopa; 3 | 4 | use mopa::Any; 5 | 6 | trait PanicAny: Any { } 7 | 8 | mopafy!(PanicAny); 9 | 10 | impl PanicAny for i32 { } 11 | 12 | fn main() { 13 | let p: &PanicAny = &2; 14 | println!("{}", p.is::()); 15 | } 16 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | // This is largely taken from the Rust distribution, with only comparatively 2 | // minor additions and alterations. Therefore, their copyright notice follows: 3 | // 4 | // Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT 5 | // file at the top-level directory of this distribution and at 6 | // http://rust-lang.org/COPYRIGHT. 7 | // 8 | // Licensed under the Apache License, Version 2.0 or the MIT license 10 | // , at your 11 | // option. This file may not be copied, modified, or distributed 12 | // except according to those terms. 13 | // 14 | // I have kept my additions under the same terms (being rather fond of MIT/Apache-2.0 myself). 15 | 16 | //! **MOPA: My Own Personal Any.** A macro to implement all the `Any` methods on your own trait. 17 | //! 18 | //! You like `Any`—its ability to store any `'static` type as a trait object and then downcast it 19 | //! back to the original type is very convenient, and in fact you need it for whatever misguided 20 | //! reason. But it’s not enough. What you *really* want is your own trait object type with `Any`’s 21 | //! functionality glued onto it. Maybe you have a `Person` trait and you want your people to be 22 | //! able to do various things, but you also want to be able to conveniently downcast the person to 23 | //! its original type, right? Alas, you can’t write a type like `Box` (at present, 24 | //! anyway). So what do you do instead? Do you give up? No, no! No, no! Enter MOPA. 25 | //! 26 | //! > There once was a quite friendly trait 27 | //! > Called `Person`, with much on its plate. 28 | //! >     “I need to be `Any` 29 | //! >     To downcast to `Benny`— 30 | //! > But I’m not, so I guess I’ll just wait.” 31 | //! 32 | //! A pitiful tale, isn’t it? Especially given that there was a bear chasing it with intent to eat 33 | //! it. Fortunately now you can *mopafy* `Person` in three simple steps: 34 | //! 35 | //! 1. Add the `mopa` crate to your `Cargo.toml` as usual and your crate root like so: 36 | //! 37 | //! ```rust 38 | //! #[macro_use] 39 | //! extern crate mopa; 40 | //! # fn main() { } 41 | //! ``` 42 | //! 43 | //! 2. Make `Any` (`mopa::Any`, not `std::any::Any`) a supertrait of `Person`; 44 | //! 45 | //! 3. `mopafy!(Person);`. 46 | //! 47 | //! And lo, you can now write `person.is::()` and `person.downcast_ref::()` and so on 48 | //! to your heart’s content. Simple, huh? 49 | //! 50 | //! Oh, by the way, it was actually the person on the bear’s plate. There wasn’t really anything on 51 | //! `Person`’s plate after all. 52 | //! 53 | //! ```rust 54 | //! #[macro_use] 55 | //! extern crate mopa; 56 | //! 57 | //! struct Bear { 58 | //! // This might be a pretty fat bear. 59 | //! fatness: u16, 60 | //! } 61 | //! 62 | //! impl Bear { 63 | //! fn eat(&mut self, person: Box) { 64 | //! self.fatness = (self.fatness as i16 + person.weight()) as u16; 65 | //! } 66 | //! } 67 | //! 68 | //! trait Person: mopa::Any { 69 | //! fn panic(&self); 70 | //! fn yell(&self) { println!("Argh!"); } 71 | //! fn sleep(&self); 72 | //! fn weight(&self) -> i16; 73 | //! } 74 | //! 75 | //! mopafy!(Person); 76 | //! 77 | //! struct Benny { 78 | //! // (Benny is not a superhero. He can’t carry more than 256kg of food at once.) 79 | //! kilograms_of_food: u8, 80 | //! } 81 | //! 82 | //! impl Person for Benny { 83 | //! fn panic(&self) { self.yell() } 84 | //! fn sleep(&self) { /* ... */ } 85 | //! fn weight(&self) -> i16 { 86 | //! // Who’s trying to find out? I’m scared! 87 | //! self.yell(); 88 | //! self.kilograms_of_food as i16 + 60 89 | //! } 90 | //! } 91 | //! 92 | //! struct Chris; 93 | //! 94 | //! impl Chris { 95 | //! // Normal people wouldn’t be brave enough to hit a bear but Chris might. 96 | //! fn hit(&self, bear: &mut Bear) { 97 | //! println!("Chris hits the bear! How brave! (Or maybe stupid?)"); 98 | //! // Meh, boundary conditions, what use are they in examples? 99 | //! // Chris clearly hits quite hard. Poor bear. 100 | //! bear.fatness -= 1; 101 | //! } 102 | //! } 103 | //! 104 | //! impl Person for Chris { 105 | //! fn panic(&self) { /* ... */ } 106 | //! fn sleep(&self) { /* ... */ } 107 | //! fn weight(&self) -> i16 { -5 /* antigravity device! cool! */ } 108 | //! } 109 | //! 110 | //! fn simulate_simulation(person: Box, bear: &mut Bear) { 111 | //! if person.is::() { 112 | //! // None of the others do, but Benny knows this particular 113 | //! // bear by reputation and he’s *really* going to be worried. 114 | //! person.yell() 115 | //! } 116 | //! // If it happens to be Chris, he’ll hit the bear. 117 | //! person.downcast_ref::().map(|chris| chris.hit(bear)); 118 | //! bear.eat(person); 119 | //! } 120 | //! 121 | //! fn main() { 122 | //! let mut bear = Bear { fatness: 10 }; 123 | //! simulate_simulation(Box::new(Benny { kilograms_of_food: 5 }), &mut bear); 124 | //! simulate_simulation(Box::new(Chris), &mut bear); 125 | //! } 126 | //! ``` 127 | //! 128 | //! Now *should* you do something like this? Probably not. Enums are probably a better solution for 129 | //! this particular case as written; frankly I believe that almost the only time you should 130 | //! downcast an `Any` trait object (or a mopafied trait object) is with a generic parameter, when 131 | //! producing something like `AnyMap`, for example. If you control *all* the code, `Any` trait 132 | //! objects are probably not the right solution; they’re good for cases with user-defined 133 | //! types across a variety of libraries. But the question of purpose and suitability is open, and I 134 | //! don’t have a really good example of such a use case here at present. TODO. 135 | 136 | #![no_std] 137 | 138 | #[cfg(test)] 139 | #[macro_use] 140 | extern crate std; 141 | 142 | /// Implementation details of the `mopafy!` macro. 143 | #[doc(hidden)] 144 | pub mod __ { 145 | pub use core::any::TypeId; 146 | // Option and Result are in the prelude, but they might have been overridden in the macro’s 147 | // scope, so we do it this way to avoid issues. (Result in particular gets overridden fairly 148 | // often.) 149 | pub use core::option::Option; 150 | pub use core::result::Result; 151 | } 152 | 153 | /// A type to emulate dynamic typing. 154 | /// 155 | /// This is a simple wrapper around `core::any::Any` which exists for [technical reasons][#27745]. 156 | /// Every type that implements `core::any::Any` implements this `Any`. 157 | /// 158 | /// See the [`core::any::Any` documentation](http://doc.rust-lang.org/core/any/trait.Any.html) for 159 | /// more details. 160 | /// 161 | /// Any traits to be mopafied must extend this trait (e.g. `trait Person: mopa::Any { }`). 162 | /// 163 | /// If/when [#27745] is resolved, this trait may be replaced with a simple reexport of 164 | /// `core::any::Any`. This will be a backwards-compatible change. 165 | /// 166 | /// [#27745]: https://github.com/rust-lang/rust/issues/27745 167 | pub trait Any: core::any::Any { 168 | /// Gets the `TypeId` of `self`. UNSTABLE; do not depend on it. 169 | #[doc(hidden)] 170 | fn __get_type_id(&self) -> __::TypeId; 171 | } 172 | 173 | impl Any for T { 174 | fn __get_type_id(&self) -> __::TypeId { 175 | __::TypeId::of::() 176 | } 177 | } 178 | 179 | /// The macro for implementing all the `Any` methods on your own trait. 180 | /// 181 | /// # Instructions for use 182 | /// 183 | /// 1. Make sure your trait extends `mopa::Any` (e.g. `trait Trait: mopa::Any { }`) 184 | /// 185 | /// 2. Mopafy your trait (see the next subsection for specifics). 186 | /// 187 | /// 3. … 188 | /// 189 | /// 4. Profit! 190 | /// 191 | /// ## Mopafication techniques 192 | /// 193 | /// There are three ways of mopafying traits, depending on what libraries you are using. 194 | /// 195 | /// 1. If you are a **normal person**: 196 | /// 197 | /// ```rust 198 | /// # #[macro_use] extern crate mopa; 199 | /// trait Trait: mopa::Any { } 200 | /// mopafy!(Trait); 201 | /// # fn main() { } 202 | /// ``` 203 | /// 204 | /// 2. If you are using **libcore** but not libstd (`#![no_std]`) or liballoc, write this: 205 | /// 206 | /// ```rust 207 | /// # #[macro_use] extern crate mopa; 208 | /// # trait Trait: mopa::Any { } 209 | /// mopafy!(Trait, only core); 210 | /// # fn main() { } 211 | /// ``` 212 | /// 213 | /// Unlike the other two techniques, this only gets you the `&Any` and `&mut Any` methods; the 214 | /// `Box` methods require liballoc. 215 | /// 216 | /// 3. If you are using **libcore and liballoc** but not libstd (`#![no_std]`), bring 217 | /// `alloc::boxed::Box` into scope and use `mopafy!` as usual: 218 | /// 219 | /// ```rust,ignore 220 | /// # // This doctest is ignored so that it doesn't break tests on the stable/beta rustc 221 | /// # // channels where #[feature] isn’t allowed. 222 | /// # #![feature(alloc)] 223 | /// # #[macro_use] extern crate mopa; 224 | /// # extern crate alloc; 225 | /// # trait Trait: mopa::Any { } 226 | /// use alloc::boxed::Box; 227 | /// mopafy!(Trait); 228 | /// # fn main() { } 229 | /// ``` 230 | #[macro_export] 231 | macro_rules! mopafy { 232 | // Implement the full suite of `Any` methods: those of `&Any`, `&mut Any` and `Box`. 233 | // 234 | // If you’re not using libstd, you’ll need to `use alloc::boxed::Box;`, or forego the 235 | // `Box` methods by just using `mopafy!(Trait, only core);`. 236 | ($trait_:ident) => { 237 | mopafy!($trait_, only core); 238 | 239 | #[allow(dead_code)] 240 | impl $trait_ { 241 | /// Returns the boxed value if it is of type `T`, or `Err(Self)` if it isn't. 242 | #[inline] 243 | pub fn downcast(self: Box) -> $crate::__::Result, Box> { 244 | if self.is::() { 245 | unsafe { 246 | $crate::__::Result::Ok(self.downcast_unchecked()) 247 | } 248 | } else { 249 | $crate::__::Result::Err(self) 250 | } 251 | } 252 | 253 | /// Returns the boxed value, blindly assuming it to be of type `T`. 254 | /// If you are not *absolutely certain* of `T`, you *must not* call this. 255 | #[inline] 256 | pub unsafe fn downcast_unchecked(self: Box) -> Box { 257 | Box::from_raw(Box::into_raw(self) as *mut T) 258 | } 259 | } 260 | }; 261 | 262 | // Not using libstd/liballoc? The core functionality can do without them; you will still have 263 | // the `&Any` and `&mut Any` methods but will lose the `Box` methods. 264 | ($trait_:ident, only core) => { 265 | #[allow(dead_code)] 266 | impl $trait_ { 267 | /// Returns true if the boxed type is the same as `T` 268 | #[inline] 269 | pub fn is(&self) -> bool { 270 | $crate::__::TypeId::of::() == $crate::Any::__get_type_id(self) 271 | } 272 | 273 | /// Returns some reference to the boxed value if it is of type `T`, or 274 | /// `None` if it isn't. 275 | #[inline] 276 | pub fn downcast_ref(&self) -> $crate::__::Option<&T> { 277 | if self.is::() { 278 | unsafe { 279 | $crate::__::Option::Some(self.downcast_ref_unchecked()) 280 | } 281 | } else { 282 | $crate::__::Option::None 283 | } 284 | } 285 | 286 | /// Returns a reference to the boxed value, blindly assuming it to be of type `T`. 287 | /// If you are not *absolutely certain* of `T`, you *must not* call this. 288 | #[inline] 289 | pub unsafe fn downcast_ref_unchecked(&self) -> &T { 290 | &*(self as *const Self as *const T) 291 | } 292 | 293 | /// Returns some mutable reference to the boxed value if it is of type `T`, or 294 | /// `None` if it isn't. 295 | #[inline] 296 | pub fn downcast_mut(&mut self) -> $crate::__::Option<&mut T> { 297 | if self.is::() { 298 | unsafe { 299 | $crate::__::Option::Some(self.downcast_mut_unchecked()) 300 | } 301 | } else { 302 | $crate::__::Option::None 303 | } 304 | } 305 | 306 | /// Returns a mutable reference to the boxed value, blindly assuming it to be of type `T`. 307 | /// If you are not *absolutely certain* of `T`, you *must not* call this. 308 | #[inline] 309 | pub unsafe fn downcast_mut_unchecked(&mut self) -> &mut T { 310 | &mut *(self as *mut Self as *mut T) 311 | } 312 | } 313 | }; 314 | } 315 | 316 | #[cfg(test)] 317 | mod tests { 318 | use std::prelude::v1::*; 319 | 320 | trait Person: super::Any { 321 | fn weight(&self) -> i16; 322 | } 323 | 324 | mopafy!(Person); 325 | 326 | #[derive(Clone, Debug, PartialEq)] 327 | struct Benny { 328 | // (Benny is not a superhero. He can’t carry more than 256kg of food at once.) 329 | kilograms_of_food: u8, 330 | } 331 | 332 | impl Person for Benny { 333 | fn weight(&self) -> i16 { 334 | self.kilograms_of_food as i16 + 60 335 | } 336 | } 337 | 338 | #[derive(Clone, Debug, PartialEq)] 339 | struct Chris; 340 | 341 | impl Person for Chris { 342 | fn weight(&self) -> i16 { -5 /* antigravity device! cool! */ } 343 | } 344 | 345 | #[test] 346 | fn test_ref() { 347 | let benny = Benny { kilograms_of_food: 13 }; 348 | let benny_ptr: *const Benny = &benny; 349 | let person: &Person = &benny; 350 | 351 | assert!(person.is::()); 352 | assert_eq!(person.downcast_ref::().map(|x| x as *const Benny), Some(benny_ptr)); 353 | assert_eq!(unsafe { person.downcast_ref_unchecked::() as *const Benny }, benny_ptr); 354 | 355 | assert!(!person.is::()); 356 | assert_eq!(person.downcast_ref::(), None); 357 | } 358 | 359 | #[test] 360 | fn test_mut() { 361 | let mut benny = Benny { kilograms_of_food: 13 }; 362 | let benny_ptr: *const Benny = &benny; 363 | let person: &mut Person = &mut benny; 364 | assert!(person.is::()); 365 | assert_eq!(person.downcast_ref::().map(|x| x as *const Benny), Some(benny_ptr)); 366 | assert_eq!(person.downcast_mut::().map(|x| &*x as *const Benny), Some(benny_ptr)); 367 | assert_eq!(unsafe { person.downcast_ref_unchecked::() as *const Benny }, benny_ptr); 368 | assert_eq!(unsafe { &*person.downcast_mut_unchecked::() as *const Benny }, benny_ptr); 369 | 370 | assert!(!person.is::()); 371 | assert_eq!(person.downcast_ref::(), None); 372 | assert_eq!(person.downcast_mut::(), None); 373 | } 374 | 375 | #[test] 376 | fn test_box() { 377 | let mut benny = Benny { kilograms_of_food: 13 }; 378 | let mut person: Box = Box::new(benny.clone()); 379 | assert!(person.is::()); 380 | assert_eq!(person.downcast_ref::(), Some(&benny)); 381 | assert_eq!(person.downcast_mut::(), Some(&mut benny)); 382 | assert_eq!(person.downcast::().map(|x| *x).ok(), Some(benny.clone())); 383 | 384 | person = Box::new(benny.clone()); 385 | assert_eq!(unsafe { person.downcast_ref_unchecked::() }, &benny); 386 | assert_eq!(unsafe { person.downcast_mut_unchecked::() }, &mut benny); 387 | assert_eq!(unsafe { *person.downcast_unchecked::() }, benny); 388 | 389 | person = Box::new(benny.clone()); 390 | assert!(!person.is::()); 391 | assert_eq!(person.downcast_ref::(), None); 392 | assert_eq!(person.downcast_mut::(), None); 393 | assert!(person.downcast::().err().is_some()); 394 | } 395 | } 396 | --------------------------------------------------------------------------------