├── .gitignore ├── Cargo.toml ├── LICENSE ├── README.md ├── constduck-procmacro ├── Cargo.toml └── src │ ├── derive.rs │ └── lib.rs └── constduck ├── Cargo.toml ├── examples ├── construct-instances.rs ├── custom-default.rs └── debug-print.rs └── src └── lib.rs /.gitignore: -------------------------------------------------------------------------------- 1 | /target 2 | Cargo.lock 3 | .vscode 4 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [workspace] 2 | members = [ 3 | "constduck", 4 | "constduck-procmacro", 5 | ] -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Mozilla Public License Version 2.0 2 | ================================== 3 | 4 | 1. Definitions 5 | -------------- 6 | 7 | 1.1. "Contributor" 8 | means each individual or legal entity that creates, contributes to 9 | the creation of, or owns Covered Software. 10 | 11 | 1.2. "Contributor Version" 12 | means the combination of the Contributions of others (if any) used 13 | by a Contributor and that particular Contributor's Contribution. 14 | 15 | 1.3. "Contribution" 16 | means Covered Software of a particular Contributor. 17 | 18 | 1.4. "Covered Software" 19 | means Source Code Form to which the initial Contributor has attached 20 | the notice in Exhibit A, the Executable Form of such Source Code 21 | Form, and Modifications of such Source Code Form, in each case 22 | including portions thereof. 23 | 24 | 1.5. "Incompatible With Secondary Licenses" 25 | means 26 | 27 | (a) that the initial Contributor has attached the notice described 28 | in Exhibit B to the Covered Software; or 29 | 30 | (b) that the Covered Software was made available under the terms of 31 | version 1.1 or earlier of the License, but not also under the 32 | terms of a Secondary License. 33 | 34 | 1.6. "Executable Form" 35 | means any form of the work other than Source Code Form. 36 | 37 | 1.7. "Larger Work" 38 | means a work that combines Covered Software with other material, in 39 | a separate file or files, that is not Covered Software. 40 | 41 | 1.8. "License" 42 | means this document. 43 | 44 | 1.9. "Licensable" 45 | means having the right to grant, to the maximum extent possible, 46 | whether at the time of the initial grant or subsequently, any and 47 | all of the rights conveyed by this License. 48 | 49 | 1.10. "Modifications" 50 | means any of the following: 51 | 52 | (a) any file in Source Code Form that results from an addition to, 53 | deletion from, or modification of the contents of Covered 54 | Software; or 55 | 56 | (b) any new file in Source Code Form that contains any Covered 57 | Software. 58 | 59 | 1.11. "Patent Claims" of a Contributor 60 | means any patent claim(s), including without limitation, method, 61 | process, and apparatus claims, in any patent Licensable by such 62 | Contributor that would be infringed, but for the grant of the 63 | License, by the making, using, selling, offering for sale, having 64 | made, import, or transfer of either its Contributions or its 65 | Contributor Version. 66 | 67 | 1.12. "Secondary License" 68 | means either the GNU General Public License, Version 2.0, the GNU 69 | Lesser General Public License, Version 2.1, the GNU Affero General 70 | Public License, Version 3.0, or any later versions of those 71 | licenses. 72 | 73 | 1.13. "Source Code Form" 74 | means the form of the work preferred for making modifications. 75 | 76 | 1.14. "You" (or "Your") 77 | means an individual or a legal entity exercising rights under this 78 | License. For legal entities, "You" includes any entity that 79 | controls, is controlled by, or is under common control with You. For 80 | purposes of this definition, "control" means (a) the power, direct 81 | or indirect, to cause the direction or management of such entity, 82 | whether by contract or otherwise, or (b) ownership of more than 83 | fifty percent (50%) of the outstanding shares or beneficial 84 | ownership of such entity. 85 | 86 | 2. License Grants and Conditions 87 | -------------------------------- 88 | 89 | 2.1. Grants 90 | 91 | Each Contributor hereby grants You a world-wide, royalty-free, 92 | non-exclusive license: 93 | 94 | (a) under intellectual property rights (other than patent or trademark) 95 | Licensable by such Contributor to use, reproduce, make available, 96 | modify, display, perform, distribute, and otherwise exploit its 97 | Contributions, either on an unmodified basis, with Modifications, or 98 | as part of a Larger Work; and 99 | 100 | (b) under Patent Claims of such Contributor to make, use, sell, offer 101 | for sale, have made, import, and otherwise transfer either its 102 | Contributions or its Contributor Version. 103 | 104 | 2.2. Effective Date 105 | 106 | The licenses granted in Section 2.1 with respect to any Contribution 107 | become effective for each Contribution on the date the Contributor first 108 | distributes such Contribution. 109 | 110 | 2.3. Limitations on Grant Scope 111 | 112 | The licenses granted in this Section 2 are the only rights granted under 113 | this License. No additional rights or licenses will be implied from the 114 | distribution or licensing of Covered Software under this License. 115 | Notwithstanding Section 2.1(b) above, no patent license is granted by a 116 | Contributor: 117 | 118 | (a) for any code that a Contributor has removed from Covered Software; 119 | or 120 | 121 | (b) for infringements caused by: (i) Your and any other third party's 122 | modifications of Covered Software, or (ii) the combination of its 123 | Contributions with other software (except as part of its Contributor 124 | Version); or 125 | 126 | (c) under Patent Claims infringed by Covered Software in the absence of 127 | its Contributions. 128 | 129 | This License does not grant any rights in the trademarks, service marks, 130 | or logos of any Contributor (except as may be necessary to comply with 131 | the notice requirements in Section 3.4). 132 | 133 | 2.4. Subsequent Licenses 134 | 135 | No Contributor makes additional grants as a result of Your choice to 136 | distribute the Covered Software under a subsequent version of this 137 | License (see Section 10.2) or under the terms of a Secondary License (if 138 | permitted under the terms of Section 3.3). 139 | 140 | 2.5. Representation 141 | 142 | Each Contributor represents that the Contributor believes its 143 | Contributions are its original creation(s) or it has sufficient rights 144 | to grant the rights to its Contributions conveyed by this License. 145 | 146 | 2.6. Fair Use 147 | 148 | This License is not intended to limit any rights You have under 149 | applicable copyright doctrines of fair use, fair dealing, or other 150 | equivalents. 151 | 152 | 2.7. Conditions 153 | 154 | Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted 155 | in Section 2.1. 156 | 157 | 3. Responsibilities 158 | ------------------- 159 | 160 | 3.1. Distribution of Source Form 161 | 162 | All distribution of Covered Software in Source Code Form, including any 163 | Modifications that You create or to which You contribute, must be under 164 | the terms of this License. You must inform recipients that the Source 165 | Code Form of the Covered Software is governed by the terms of this 166 | License, and how they can obtain a copy of this License. You may not 167 | attempt to alter or restrict the recipients' rights in the Source Code 168 | Form. 169 | 170 | 3.2. Distribution of Executable Form 171 | 172 | If You distribute Covered Software in Executable Form then: 173 | 174 | (a) such Covered Software must also be made available in Source Code 175 | Form, as described in Section 3.1, and You must inform recipients of 176 | the Executable Form how they can obtain a copy of such Source Code 177 | Form by reasonable means in a timely manner, at a charge no more 178 | than the cost of distribution to the recipient; and 179 | 180 | (b) You may distribute such Executable Form under the terms of this 181 | License, or sublicense it under different terms, provided that the 182 | license for the Executable Form does not attempt to limit or alter 183 | the recipients' rights in the Source Code Form under this License. 184 | 185 | 3.3. Distribution of a Larger Work 186 | 187 | You may create and distribute a Larger Work under terms of Your choice, 188 | provided that You also comply with the requirements of this License for 189 | the Covered Software. If the Larger Work is a combination of Covered 190 | Software with a work governed by one or more Secondary Licenses, and the 191 | Covered Software is not Incompatible With Secondary Licenses, this 192 | License permits You to additionally distribute such Covered Software 193 | under the terms of such Secondary License(s), so that the recipient of 194 | the Larger Work may, at their option, further distribute the Covered 195 | Software under the terms of either this License or such Secondary 196 | License(s). 197 | 198 | 3.4. Notices 199 | 200 | You may not remove or alter the substance of any license notices 201 | (including copyright notices, patent notices, disclaimers of warranty, 202 | or limitations of liability) contained within the Source Code Form of 203 | the Covered Software, except that You may alter any license notices to 204 | the extent required to remedy known factual inaccuracies. 205 | 206 | 3.5. Application of Additional Terms 207 | 208 | You may choose to offer, and to charge a fee for, warranty, support, 209 | indemnity or liability obligations to one or more recipients of Covered 210 | Software. However, You may do so only on Your own behalf, and not on 211 | behalf of any Contributor. You must make it absolutely clear that any 212 | such warranty, support, indemnity, or liability obligation is offered by 213 | You alone, and You hereby agree to indemnify every Contributor for any 214 | liability incurred by such Contributor as a result of warranty, support, 215 | indemnity or liability terms You offer. You may include additional 216 | disclaimers of warranty and limitations of liability specific to any 217 | jurisdiction. 218 | 219 | 4. Inability to Comply Due to Statute or Regulation 220 | --------------------------------------------------- 221 | 222 | If it is impossible for You to comply with any of the terms of this 223 | License with respect to some or all of the Covered Software due to 224 | statute, judicial order, or regulation then You must: (a) comply with 225 | the terms of this License to the maximum extent possible; and (b) 226 | describe the limitations and the code they affect. Such description must 227 | be placed in a text file included with all distributions of the Covered 228 | Software under this License. Except to the extent prohibited by statute 229 | or regulation, such description must be sufficiently detailed for a 230 | recipient of ordinary skill to be able to understand it. 231 | 232 | 5. Termination 233 | -------------- 234 | 235 | 5.1. The rights granted under this License will terminate automatically 236 | if You fail to comply with any of its terms. However, if You become 237 | compliant, then the rights granted under this License from a particular 238 | Contributor are reinstated (a) provisionally, unless and until such 239 | Contributor explicitly and finally terminates Your grants, and (b) on an 240 | ongoing basis, if such Contributor fails to notify You of the 241 | non-compliance by some reasonable means prior to 60 days after You have 242 | come back into compliance. Moreover, Your grants from a particular 243 | Contributor are reinstated on an ongoing basis if such Contributor 244 | notifies You of the non-compliance by some reasonable means, this is the 245 | first time You have received notice of non-compliance with this License 246 | from such Contributor, and You become compliant prior to 30 days after 247 | Your receipt of the notice. 248 | 249 | 5.2. If You initiate litigation against any entity by asserting a patent 250 | infringement claim (excluding declaratory judgment actions, 251 | counter-claims, and cross-claims) alleging that a Contributor Version 252 | directly or indirectly infringes any patent, then the rights granted to 253 | You by any and all Contributors for the Covered Software under Section 254 | 2.1 of this License shall terminate. 255 | 256 | 5.3. In the event of termination under Sections 5.1 or 5.2 above, all 257 | end user license agreements (excluding distributors and resellers) which 258 | have been validly granted by You or Your distributors under this License 259 | prior to termination shall survive termination. 260 | 261 | ************************************************************************ 262 | * * 263 | * 6. Disclaimer of Warranty * 264 | * ------------------------- * 265 | * * 266 | * Covered Software is provided under this License on an "as is" * 267 | * basis, without warranty of any kind, either expressed, implied, or * 268 | * statutory, including, without limitation, warranties that the * 269 | * Covered Software is free of defects, merchantable, fit for a * 270 | * particular purpose or non-infringing. The entire risk as to the * 271 | * quality and performance of the Covered Software is with You. * 272 | * Should any Covered Software prove defective in any respect, You * 273 | * (not any Contributor) assume the cost of any necessary servicing, * 274 | * repair, or correction. This disclaimer of warranty constitutes an * 275 | * essential part of this License. No use of any Covered Software is * 276 | * authorized under this License except under this disclaimer. * 277 | * * 278 | ************************************************************************ 279 | 280 | ************************************************************************ 281 | * * 282 | * 7. Limitation of Liability * 283 | * -------------------------- * 284 | * * 285 | * Under no circumstances and under no legal theory, whether tort * 286 | * (including negligence), contract, or otherwise, shall any * 287 | * Contributor, or anyone who distributes Covered Software as * 288 | * permitted above, be liable to You for any direct, indirect, * 289 | * special, incidental, or consequential damages of any character * 290 | * including, without limitation, damages for lost profits, loss of * 291 | * goodwill, work stoppage, computer failure or malfunction, or any * 292 | * and all other commercial damages or losses, even if such party * 293 | * shall have been informed of the possibility of such damages. This * 294 | * limitation of liability shall not apply to liability for death or * 295 | * personal injury resulting from such party's negligence to the * 296 | * extent applicable law prohibits such limitation. Some * 297 | * jurisdictions do not allow the exclusion or limitation of * 298 | * incidental or consequential damages, so this exclusion and * 299 | * limitation may not apply to You. * 300 | * * 301 | ************************************************************************ 302 | 303 | 8. Litigation 304 | ------------- 305 | 306 | Any litigation relating to this License may be brought only in the 307 | courts of a jurisdiction where the defendant maintains its principal 308 | place of business and such litigation shall be governed by laws of that 309 | jurisdiction, without reference to its conflict-of-law provisions. 310 | Nothing in this Section shall prevent a party's ability to bring 311 | cross-claims or counter-claims. 312 | 313 | 9. Miscellaneous 314 | ---------------- 315 | 316 | This License represents the complete agreement concerning the subject 317 | matter hereof. If any provision of this License is held to be 318 | unenforceable, such provision shall be reformed only to the extent 319 | necessary to make it enforceable. Any law or regulation which provides 320 | that the language of a contract shall be construed against the drafter 321 | shall not be used to construe this License against a Contributor. 322 | 323 | 10. Versions of the License 324 | --------------------------- 325 | 326 | 10.1. New Versions 327 | 328 | Mozilla Foundation is the license steward. Except as provided in Section 329 | 10.3, no one other than the license steward has the right to modify or 330 | publish new versions of this License. Each version will be given a 331 | distinguishing version number. 332 | 333 | 10.2. Effect of New Versions 334 | 335 | You may distribute the Covered Software under the terms of the version 336 | of the License under which You originally received the Covered Software, 337 | or under the terms of any subsequent version published by the license 338 | steward. 339 | 340 | 10.3. Modified Versions 341 | 342 | If you create software not governed by this License, and you want to 343 | create a new license for such software, you may create and use a 344 | modified version of this License if you rename the license and remove 345 | any references to the name of the license steward (except to note that 346 | such modified license differs from this License). 347 | 348 | 10.4. Distributing Source Code Form that is Incompatible With Secondary 349 | Licenses 350 | 351 | If You choose to distribute Source Code Form that is Incompatible With 352 | Secondary Licenses under the terms of this version of the License, the 353 | notice described in Exhibit B of this License must be attached. 354 | 355 | Exhibit A - Source Code Form License Notice 356 | ------------------------------------------- 357 | 358 | This Source Code Form is subject to the terms of the Mozilla Public 359 | License, v. 2.0. If a copy of the MPL was not distributed with this 360 | file, You can obtain one at http://mozilla.org/MPL/2.0/. 361 | 362 | If it is not possible or desirable to put the notice in a particular 363 | file, then You may include the notice in a location (such as a LICENSE 364 | file in a relevant directory) where a recipient would be likely to look 365 | for such a notice. 366 | 367 | You may add additional accurate notices of copyright ownership. 368 | 369 | Exhibit B - "Incompatible With Secondary Licenses" Notice 370 | --------------------------------------------------------- 371 | 372 | This Source Code Form is "Incompatible With Secondary Licenses", as 373 | defined by the Mozilla Public License, v. 2.0. 374 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | [![crates.io](https://img.shields.io/crates/v/constduck.svg)](https://crates.io/crates/constduck/) [![docs](https://img.shields.io/badge/docs-rs.svg)](https://docs.rs/constduck/) 2 | 3 | # `constduck`: compile-time duck typing and reflection 4 | `constduck` provides a procmacro that can enable compile time duck typing and reflection on arbitrary struct types. It supports three main features: 5 | 6 | * Accessing fields of any struct, using the field name 7 | * Constructing instances from a mapping of fields to values 8 | * Reflecting over field types at compile time 9 | 10 | # Usage 11 | Derive `ConstDuck` on a struct: 12 | ```rust 13 | #![feature(adt_const_params)] 14 | use constduck::*; 15 | 16 | #[derive(ConstDuck)] 17 | struct Donald { 18 | money: i64, 19 | } 20 | ``` 21 | 22 | ## Accessing fields 23 | When deriving `ConstDuck`, the trait `Field<"fieldname">` is implemented for all fields of the struct. You can use the trait to write generic implementations. For example: 24 | 25 | ```rust 26 | fn deduct_money>(t: &mut T) 27 | where N: Clone, 28 | N: Sub, 29 | N: From { 30 | t.set(t.get().clone() - N::from(5i8)); 31 | } 32 | ``` 33 | 34 | `deduct_money` will work for any struct that has a field `money` and derives `ConstDuck`. 35 | 36 | You should just write a custom trait for the example above. It's not always possible to write a custom trait. For example, consider the following macro: 37 | 38 | ```rust 39 | macro_rules! make_getter { 40 | ($struct:ident.$field:ident) => { 41 | impl $struct { 42 | pub fn $field(&self) -> &/* What to write here? */ { 43 | &self.$field 44 | } 45 | } 46 | } 47 | } 48 | 49 | struct Foo { 50 | bar: String, 51 | baz: u32, 52 | } 53 | 54 | make_getter!(Foo.bar); 55 | ``` 56 | 57 | In this case the function definition requires a return type, but you don't have enough information to specify the type. Using `constduck`, you can write this macro as: 58 | 59 | ```rust 60 | macro_rules! make_getter { 61 | ($struct:ident.$field:ident) => { 62 | impl $struct 63 | where Self: Field<{ stringify!($field) }, Ty = T> { 64 | pub fn $field(&self) -> &T { 65 | >::get(self) 66 | } 67 | } 68 | } 69 | } 70 | 71 | #[derive(ConstDuck)] 72 | struct Foo { 73 | bar: String, 74 | baz: u32, 75 | } 76 | 77 | make_getter!(Foo.bar); 78 | ``` 79 | 80 | ## Constructing instances 81 | If you're storing arbitrary expressions in a new struct in a macro, you cannot use the type of the expression for the field. For example: 82 | 83 | ```rust 84 | macro_rules! create_struct { 85 | ($struct:ident; $($name:ident: $value:expr),*) => {{ 86 | // For some good reason we want to generate a separate wrapper struct first and return that instead of collecting directly into `$struct`. 87 | struct WrapperStruct<$($name,)*> { 88 | $($name: $name,)* 89 | } 90 | 91 | impl<$($name,)*> From> for $struct { 92 | fn from(wrapper: WrapperStruct<$($name,)*>) -> Self { 93 | // wrapper.counter is not guaranteed to be a u32 94 | // So we cannot do this: 95 | $struct { 96 | counter: wrapper.counter, 97 | text: wrapper.text, 98 | } 99 | } 100 | } 101 | 102 | WrapperStruct { 103 | $($name: $value,)* 104 | } 105 | }} 106 | } 107 | ``` 108 | 109 | We cannot write a correct implementation for `From` here, because it's normally not possible to express "type must have two fields `counter: u32` and `text: String`" as a constraint. 110 | 111 | By implementing `WithField` for the wrapper struct, we can write the implementation in the macro like this instead: 112 | 113 | ```rust 114 | impl<$($name,)*> From> for $struct 115 | where $struct: ConstructFrom> { 116 | fn from(wrapper: WrapperStruct<$($name,)*>) -> Self { 117 | $struct::construct(wrapper) 118 | } 119 | } 120 | ``` 121 | 122 | See [`constduck/examples/construct-instances.rs`](constduck/examples/construct-instances.rs) for a full example. 123 | 124 | ## Reflecting over field types at compile time 125 | 126 | Using `ConstDuck::Reflect` you can implement traits for any type (like `#[derive(..)]`) without needing a procmacro. See [`constduck/examples/debug-print.rs`](constduck/examples/debug-print.rs) for an example. 127 | 128 | # (In)stability 129 | This project requires Rust nightly, and uses the incomplete `adt_const_params` feature. You might encounter ICEs. 130 | The current API will likely break when support for tuple structs and enums is added. 131 | 132 | # License 133 | `constduck` is licensed under the Mozilla Public License 2.0 (MPL2.0). See the [`LICENSE`](LICENSE) file. -------------------------------------------------------------------------------- /constduck-procmacro/Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "constduck-procmacro" 3 | version = "0.1.0" 4 | edition = "2021" 5 | authors = ["ferrouille "] 6 | license = "MPL-2.0" 7 | repository = "https://github.com/ferrouille/constduck" 8 | description = "Macro implementation of #[derive(ConstDuck)]" 9 | 10 | [lib] 11 | proc-macro = true 12 | 13 | [dependencies] 14 | syn = { version = "1.0.5", features = ["derive", "printing"] } 15 | proc-macro2 = "1.0.30" 16 | quote = "1.0" -------------------------------------------------------------------------------- /constduck-procmacro/src/derive.rs: -------------------------------------------------------------------------------- 1 | use proc_macro2::{Punct, Spacing, Span, TokenStream, TokenTree}; 2 | use quote::{format_ident, ToTokens}; 3 | use syn::{Data, DeriveInput, LitStr}; 4 | 5 | pub fn gen(input: &DeriveInput) -> TokenStream { 6 | let ident = input.ident.clone(); 7 | if let Data::Struct(s) = &input.data { 8 | let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl(); 9 | 10 | let mut tokens = TokenStream::new(); 11 | for field in s.fields.iter() { 12 | let fieldident = field 13 | .ident 14 | .as_ref() 15 | .expect("All fields must have names") 16 | .clone(); 17 | let fieldname = fieldident.to_string(); 18 | let ty = field.ty.clone(); 19 | tokens.extend(quote::quote! { 20 | #[automatically_derived] 21 | impl #impl_generics ::constduck::Field<#fieldname> for #ident #ty_generics #where_clause { 22 | type Ty = #ty; 23 | 24 | fn get(&self) -> &Self::Ty { 25 | &self.#fieldident 26 | } 27 | 28 | fn get_consume(self) -> Self::Ty { 29 | self.#fieldident 30 | } 31 | 32 | fn set(&mut self, new_value: Self::Ty) { 33 | self.#fieldident = new_value; 34 | } 35 | } 36 | }); 37 | } 38 | 39 | let fieldidents = s 40 | .fields 41 | .iter() 42 | .map(|field| field.ident.as_ref().expect("All fields must have names")) 43 | .collect::>(); 44 | let fieldnames = s 45 | .fields 46 | .iter() 47 | .map(|field| field.ident.as_ref().expect("All fields must have names")) 48 | .map(|ident| LitStr::new(&ident.to_string(), Span::call_site())) 49 | .collect::>(); 50 | let fieldtypes = s 51 | .fields 52 | .iter() 53 | .map(|field| field.ty.clone()) 54 | .collect::>(); 55 | let gs = s 56 | .fields 57 | .iter() 58 | .enumerate() 59 | .map(|(n, _)| format_ident!("__K{}", n)) 60 | .collect::>(); 61 | 62 | let mut field_iter = quote::quote! { ::constduck::FieldListNil }; 63 | for fieldname in fieldnames.iter().rev() { 64 | field_iter = quote::quote! { 65 | ::constduck::FieldListCons<#fieldname, #field_iter> 66 | }; 67 | } 68 | 69 | // Strip < and > from the generics 70 | let generics_base = impl_generics.to_token_stream(); 71 | let mut gens = TokenStream::new(); 72 | let mut first = true; 73 | let mut prev = None; 74 | for token in generics_base { 75 | if first { 76 | first = false; 77 | } else { 78 | if let Some(prev) = prev { 79 | gens.extend([prev]); 80 | } 81 | 82 | prev = Some(token); 83 | } 84 | } 85 | 86 | if !gens.is_empty() { 87 | gens.extend([TokenTree::Punct(Punct::new(',', Spacing::Alone))]); 88 | } 89 | 90 | let field_iter = quote::quote! { ::constduck::Struct<#field_iter> }; 91 | let structname = ident.to_string(); 92 | tokens.extend(quote::quote! { 93 | impl<#gens #(#gs: Into<#fieldtypes>,)* __D: #(::constduck::WithField<#fieldnames, Output = #gs> +)*> ::constduck::ConstructFrom<__D> for #ident #ty_generics #where_clause { 94 | fn construct(data: __D) -> Self { 95 | Self { 96 | #( 97 | #fieldidents: <__D as ::constduck::WithField<{ #fieldnames }>>::value(&data).into(), 98 | )* 99 | } 100 | } 101 | } 102 | 103 | #[automatically_derived] 104 | impl #impl_generics ::constduck::ConstDuck for #ident #ty_generics #where_clause { 105 | const NAME: &'static str = #structname; 106 | type Reflect = #field_iter; 107 | } 108 | 109 | #[automatically_derived] 110 | impl<#gens __T> ::constduck::ConstDuckGeneric<__T> for #ident #ty_generics #where_clause { 111 | const NAME: &'static str = #structname; 112 | type Reflect = #field_iter; 113 | } 114 | }); 115 | 116 | tokens 117 | } else { 118 | unreachable!() 119 | } 120 | } 121 | -------------------------------------------------------------------------------- /constduck-procmacro/src/lib.rs: -------------------------------------------------------------------------------- 1 | use syn::{parse_macro_input, DeriveInput}; 2 | 3 | mod derive; 4 | 5 | #[proc_macro_derive(ConstDuck)] 6 | pub fn derive_field_names(input: proc_macro::TokenStream) -> proc_macro::TokenStream { 7 | let input = parse_macro_input!(input as DeriveInput); 8 | derive::gen(&input).into() 9 | } 10 | -------------------------------------------------------------------------------- /constduck/Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "constduck" 3 | version = "0.1.0" 4 | edition = "2021" 5 | authors = ["ferrouille "] 6 | license = "MPL-2.0" 7 | repository = "https://github.com/ferrouille/constduck" 8 | description = "Compile-time ducktyping and reflection using const generics" 9 | readme = "../README.md" 10 | exclude = ["examples"] 11 | 12 | [dependencies] 13 | constduck-procmacro = { path = "../constduck-procmacro/", version = "0.1" } -------------------------------------------------------------------------------- /constduck/examples/construct-instances.rs: -------------------------------------------------------------------------------- 1 | use constduck::{ConstDuck, ConstructFrom, WithField}; 2 | 3 | #[derive(ConstDuck, Debug)] 4 | struct Foo { 5 | counter: u32, 6 | text: String, 7 | } 8 | 9 | macro_rules! create_struct { 10 | (@genmapping $firstname:ident: $firstvalue:expr, $($name:ident: $value:expr,)* { $($name2:ident: $value2:expr,)* }) => { 11 | #[allow(non_camel_case_types)] 12 | impl<$($name2,)*> WithField<{ stringify!($firstname) }> for WrapperStruct<$($name2,)*> 13 | where $firstname: Clone { 14 | type Output = $firstname; 15 | 16 | fn value(&self) -> Self::Output { 17 | self.$firstname.clone() 18 | } 19 | } 20 | 21 | create_struct!(@genmapping $($name: $value,)* { $($name2: $value2,)* }); 22 | }; 23 | (@genmapping { $($name2:ident: $value2:expr,)* }) => {}; 24 | ($struct:ident; $($name:ident: $value:expr),*) => {{ 25 | #[allow(non_camel_case_types)] 26 | struct WrapperStruct<$($name,)*> { 27 | $($name: $name,)* 28 | } 29 | 30 | create_struct!(@genmapping $($name: $value,)* { $($name: $value,)* }); 31 | 32 | #[allow(non_camel_case_types)] 33 | impl<$($name,)*> From> for $struct 34 | where $struct: ConstructFrom> { 35 | fn from(wrapper: WrapperStruct<$($name,)*>) -> Self { 36 | // We cannot do this: 37 | // 38 | // $struct { 39 | // counter: wrapper.counter, 40 | // text: wrapper.text, 41 | // } 42 | // 43 | // Because wrapper.counter is not guaranteed to be a u32, and $struct might not contain the same fields. 44 | 45 | $struct::construct(wrapper) 46 | } 47 | } 48 | 49 | WrapperStruct { 50 | $($name: $value,)* 51 | } 52 | }} 53 | } 54 | 55 | fn main() { 56 | let foo = create_struct!( 57 | Foo; 58 | counter: 5u32, 59 | text: String::new() 60 | ); 61 | 62 | let real_foo: Foo = foo.into(); 63 | println!("Foo: {:?}", real_foo); 64 | } 65 | -------------------------------------------------------------------------------- /constduck/examples/custom-default.rs: -------------------------------------------------------------------------------- 1 | #![allow(incomplete_features)] 2 | #![feature(adt_const_params)] 3 | 4 | use constduck::{ConstDuck, ConstructFrom, Field, WithField}; 5 | use std::marker::PhantomData; 6 | 7 | #[derive(PartialEq, Debug)] 8 | struct Money(i64); 9 | 10 | #[derive(PartialEq, Debug, ConstDuck)] 11 | struct Donald { 12 | name: String, 13 | money: Money, 14 | } 15 | 16 | #[derive(PartialEq, Debug, ConstDuck)] 17 | struct Pond { 18 | d1: Donald, 19 | d2: Donald, 20 | d3: Donald, 21 | } 22 | 23 | #[derive(ConstDuck)] 24 | struct Foo> { 25 | t: T, 26 | } 27 | 28 | // A custom implementation for `Default`. 29 | pub trait MyDefault { 30 | fn default() -> Self; 31 | } 32 | 33 | // Helper struct. 34 | pub struct CreateDefault(PhantomData); 35 | 36 | // `CreateDefault` implements `WithField` for all possible fields. 37 | // All fields must be types for which `MyDefault` is also implemented. 38 | impl WithField for CreateDefault 39 | where 40 | T: Field, 41 | T::Ty: MyDefault, 42 | { 43 | type Output = T::Ty; 44 | 45 | fn value(&self) -> Self::Output { 46 | // To obtain a value for the field, we invoke `MyDefault::default`. 47 | T::Ty::default() 48 | } 49 | } 50 | 51 | // MyDefault 'leaf' implementations for `String` and `Money` 52 | impl MyDefault for String { 53 | fn default() -> Self { 54 | "".to_string() 55 | } 56 | } 57 | 58 | impl MyDefault for Money { 59 | fn default() -> Self { 60 | Money(5) 61 | } 62 | } 63 | 64 | // A MyDefault implementation for any type that implements `CreateDefault`. 65 | // Any type that derives `ConstDuck` implements `CreateDefault` for `T: WithField + WithField + ...`. 66 | impl>> MyDefault for T { 67 | fn default() -> Self { 68 | Self::construct(CreateDefault(PhantomData)) 69 | } 70 | } 71 | 72 | pub fn main() { 73 | println!("Duckburg: {:#?}", ::default()); 74 | } 75 | 76 | #[cfg(test)] 77 | mod tests { 78 | use crate::*; 79 | use constduck::Field; 80 | 81 | #[test] 82 | fn field_access() { 83 | let duck = Donald { 84 | name: "Donald".to_string(), 85 | money: Money(-42), 86 | }; 87 | 88 | assert_eq!(>::get(&duck), "Donald"); 89 | assert_eq!(>::get(&duck), &Money(-42)); 90 | assert_eq!(>::get_consume(duck), Money(-42)); 91 | } 92 | 93 | #[test] 94 | fn my_default() { 95 | let duck = ::default(); 96 | assert_eq!( 97 | duck, 98 | Donald { 99 | name: String::new(), 100 | money: Money(5), 101 | } 102 | ); 103 | 104 | let pond = ::default(); 105 | assert_eq!( 106 | pond, 107 | Pond { 108 | d1: Donald { 109 | name: String::new(), 110 | money: Money(5), 111 | }, 112 | d2: Donald { 113 | name: String::new(), 114 | money: Money(5), 115 | }, 116 | d3: Donald { 117 | name: String::new(), 118 | money: Money(5), 119 | }, 120 | } 121 | ); 122 | } 123 | } 124 | -------------------------------------------------------------------------------- /constduck/examples/debug-print.rs: -------------------------------------------------------------------------------- 1 | #![allow(incomplete_features)] 2 | #![feature(adt_const_params)] 3 | 4 | use constduck::{ 5 | ConstDuck, ConstDuckGeneric, Field, FieldList, FieldListCons, FieldListNil, Struct, 6 | }; 7 | use std::fmt; 8 | 9 | // Some boring formatting stuff 10 | #[derive(Copy, Clone)] 11 | struct Indent { 12 | n: usize, 13 | } 14 | 15 | impl Indent { 16 | pub fn next(&self) -> Indent { 17 | Indent { n: self.n + 1 } 18 | } 19 | 20 | pub fn new() -> Indent { 21 | Indent { n: 0 } 22 | } 23 | } 24 | 25 | impl fmt::Display for Indent { 26 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { 27 | for _ in 0..self.n { 28 | write!(f, " ")?; 29 | } 30 | 31 | Ok(()) 32 | } 33 | } 34 | 35 | // The trait we're going to implement. 36 | // MyPrint will simply print all the fields of a struct to stdout, recursively. 37 | trait MyPrint { 38 | fn print(&self, indent: Indent); 39 | } 40 | 41 | // Implementations for some basic types 42 | impl MyPrint for &'static str { 43 | fn print(&self, indent: Indent) { 44 | println!("{}&'static str = {:?}", indent, self); 45 | } 46 | } 47 | 48 | impl MyPrint for u32 { 49 | fn print(&self, indent: Indent) { 50 | println!("{}u32 = {}", indent, self); 51 | } 52 | } 53 | 54 | // Implementation guard to make sure nobody else can implement conflicting implementations. 55 | struct ImplGuard; 56 | 57 | // Helper trait for printing fields in a field list 58 | trait PrintHelper { 59 | fn print(obj: &O, indent: Indent); 60 | } 61 | 62 | impl PrintHelper for FieldListNil { 63 | fn print(_: &O, _: Indent) {} 64 | } 65 | 66 | // `MyPrint` implementation for a struct 67 | impl> PrintHelper for Struct { 68 | fn print(obj: &O, indent: Indent) { 69 | L::print(obj, indent); 70 | } 71 | } 72 | 73 | impl PrintHelper for FieldListCons 74 | where 75 | O: Field, 76 | O::Ty: MyPrint, 77 | T: PrintHelper, 78 | { 79 | fn print(obj: &O, indent: Indent) { 80 | println!("{}Field `{}`", indent, NAME); 81 | obj.get().print(indent.next()); 82 | T::print(obj, indent); 83 | } 84 | } 85 | 86 | // `MyPrint` implementation for all types that derive `ConstDuck`. 87 | impl> MyPrint for T 88 | where 89 | >::Reflect: PrintHelper, 90 | { 91 | fn print(&self, indent: Indent) { 92 | println!("{}struct `{}`:", indent, T::NAME); 93 | 94 | >::print(&self, indent.next()) 95 | } 96 | } 97 | 98 | fn main() { 99 | // Derive ConstDuck for some types 100 | #[derive(ConstDuck)] 101 | struct Foo { 102 | bar: Bar, 103 | baz: Baz, 104 | } 105 | 106 | #[derive(ConstDuck)] 107 | struct Bar { 108 | life: u32, 109 | is_like: &'static str, 110 | a: u32, 111 | } 112 | 113 | #[derive(ConstDuck)] 114 | struct Baz { 115 | hurricane: &'static str, 116 | } 117 | 118 | // Use MyPrint for a simple type 119 | let baz = Baz { hurricane: "Hello" }; 120 | baz.print(Indent::new()); 121 | 122 | // Use MyPrint for a more complex type 123 | let foo = Foo { 124 | bar: Bar { 125 | life: 16, 126 | is_like: "Hello, world!", 127 | a: 100_234, 128 | }, 129 | baz: Baz { 130 | hurricane: "Hello, world!", 131 | }, 132 | }; 133 | foo.print(Indent::new()); 134 | } 135 | -------------------------------------------------------------------------------- /constduck/src/lib.rs: -------------------------------------------------------------------------------- 1 | #![allow(incomplete_features)] 2 | #![feature(adt_const_params)] 3 | #![feature(inherent_associated_types)] 4 | 5 | //! `constduck` implements compile-time duck typing via const generics. 6 | //! It only works on structs. 7 | //! 8 | //! **Note:** if you can, use a custom trait instead of `constduck`. 9 | //! Only use `constduck` in cases where you can't implement a custom trait. 10 | //! 11 | //! You must `#[derive(ConstDuck)]` on all traits that you want to duck-type. 12 | //! For example: 13 | //! ```rust 14 | //! # #![feature(adt_const_params)] 15 | //! # use constduck::*; 16 | //! #[derive(ConstDuck)] 17 | //! struct Donald { 18 | //! money: i64, 19 | //! } 20 | //! ``` 21 | //! 22 | //! This implements [`Field<"money">`](Field) and [`ConstructFrom>`](ConstructFrom) for `Donald`. 23 | //! 24 | //! You can use `constduck` to derive implementations for traits, like #[derive(..)]. 25 | //! See [constduck/examples/debug-print.rs] for an example. 26 | //! The example implements a trait (`MyPrint`) for all types that derive `ConstDuck`. 27 | //! 28 | //! You can use [`Field::get`], [`Field::get_consume`] and [`Field::set`] to access the fields of the struct. For example: 29 | //! 30 | //! ```rust 31 | //! # #![feature(adt_const_params)] 32 | //! # use constduck::*; 33 | //! use std::ops::Sub; 34 | //! 35 | //! #[derive(ConstDuck)] 36 | //! struct Donald { 37 | //! money: i8, 38 | //! } 39 | //! 40 | //! #[derive(ConstDuck)] 41 | //! struct Scrooge { 42 | //! money: i64, 43 | //! } 44 | //! 45 | //! let mut donald = Donald { money: 5 }; 46 | //! let mut scrooge = Scrooge { money: 1_000_000_000 }; 47 | //! 48 | //! fn deduct_money>(t: &mut T) 49 | //! where N: Clone, 50 | //! N: Sub, 51 | //! N: From { 52 | //! t.set(t.get().clone() - N::from(5i8)); 53 | //! } 54 | //! 55 | //! assert_eq!(donald.money, 5); 56 | //! deduct_money(&mut donald); 57 | //! assert_eq!(donald.money, 0); 58 | //! 59 | //! assert_eq!(scrooge.money, 1_000_000_000); 60 | //! deduct_money(&mut scrooge); 61 | //! assert_eq!(scrooge.money, 0_999_999_995); 62 | //! ``` 63 | //! 64 | //! The main use case for `constduck` is in macros. 65 | //! You sometimes need to specify a type in a macro. 66 | //! If you only know the type of the struct, it is normally impossible to obtain the type of a field. 67 | //! With `constduck`, you can write this type using generics. For example: 68 | //! 69 | //! ```rust 70 | //! # #![feature(adt_const_params)] 71 | //! # use constduck::*; 72 | //! macro_rules! make_getter { 73 | //! ($struct:ident.$field:ident) => { 74 | //! impl $struct 75 | //! where Self: Field<{ stringify!($field) }, Ty = T> { 76 | //! pub fn $field(&self) -> &T { 77 | //! >::get(self) 78 | //! } 79 | //! } 80 | //! } 81 | //! } 82 | //! 83 | //! #[derive(ConstDuck)] 84 | //! struct Foo { 85 | //! bar: String, 86 | //! baz: u32, 87 | //! } 88 | //! 89 | //! make_getter!(Foo.bar); 90 | //! ``` 91 | 92 | /// Derives [`Field`] for each field of a struct and [`ConstructFrom`]. 93 | /// `ConstructFrom` is derived for `T`s that implement [`WithField`]. 94 | /// For example, if a struct `foo` has fields `bar` and `baz`, 95 | /// `ConstructFrom` will be implemented for all `T: WithField<"bar"> + WithField<"baz">`. 96 | pub use constduck_procmacro::ConstDuck; 97 | 98 | /// Trait that provides compile-time type info for the type's fields. 99 | pub trait ConstDuck { 100 | /// The name of the type 101 | const NAME: &'static str; 102 | 103 | /// The type used for reflection: a [`Struct`](Struct). 104 | type Reflect; 105 | } 106 | 107 | /// The reflection type of a normal struct. L is a list of fields in the same order as the definition. 108 | pub struct Struct(L); 109 | 110 | impl Struct { 111 | type Fields = L; 112 | } 113 | 114 | /// Identical to [`ConstDuck`], implemented for all `T`. 115 | /// This trait can be helpful when implementing your own trait for all types that implement ConstDuck. 116 | /// For example, let's say we want to implement a custom trait `MyTrait`. 117 | /// We provide a custom implementation for `u32`: `impl MyTrait for u32 { .. }`. 118 | /// Now we cannot implement `MyTrait` for all `T: ConstDuck` anymore. 119 | /// We *can* still `impl> MyTrait for T`, if `ImplGuard` is a local type. 120 | /// 121 | /// I don't understand this well enough to explain why this works. 122 | /// See [Rust's orphan rules](https://github.com/rust-lang/rfcs/blob/master/text/2451-re-rebalancing-coherence.md). 123 | pub trait ConstDuckGeneric { 124 | const NAME: &'static str; 125 | type Reflect; 126 | } 127 | 128 | /// A list of fields, available at compile time. 129 | pub trait FieldList {} 130 | 131 | /// The first entry in the list (`HEAD`) and the tail of the [`FieldList`]. 132 | pub struct FieldListCons(T); 133 | 134 | /// The end of the [`FieldList`]. 135 | pub struct FieldListNil; 136 | 137 | impl FieldList for FieldListCons {} 138 | impl FieldList for FieldListNil {} 139 | 140 | /// `Field` is normally implemented for structs that have a field named `NAME`. 141 | /// Access to the field's value is provided via [`Field::get`], [`Field::get_consume`] and [`Field::set`]. 142 | pub trait Field { 143 | type Ty; 144 | 145 | fn get(&self) -> &Self::Ty; 146 | fn get_consume(self) -> Self::Ty; 147 | fn set(&mut self, value: Self::Ty); 148 | } 149 | 150 | /// `WithField` indicates that a type can create a new value for a field named `NAME`. 151 | /// This trait is used for [`ConstructFrom`]. See [`ConstDuck`]. 152 | pub trait WithField { 153 | type Output; 154 | 155 | fn value(&self) -> Self::Output; 156 | } 157 | 158 | /// When a type implements `ConstructFrom`, a new instance of the type can be constructed from a `T`. 159 | pub trait ConstructFrom { 160 | fn construct(t: T) -> Self; 161 | } 162 | --------------------------------------------------------------------------------