├── .clippy.toml ├── .github └── workflows │ └── ci.yml ├── .gitignore ├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── README.md ├── src └── lib.rs └── tests └── readme.rs /.clippy.toml: -------------------------------------------------------------------------------- 1 | msrv = "1.36.0" 2 | -------------------------------------------------------------------------------- /.github/workflows/ci.yml: -------------------------------------------------------------------------------- 1 | name: CI 2 | 3 | on: 4 | push: 5 | pull_request: 6 | schedule: [cron: "40 1 * * *"] 7 | 8 | permissions: 9 | contents: read 10 | 11 | env: 12 | RUSTFLAGS: -Dwarnings 13 | 14 | jobs: 15 | test: 16 | name: Rust ${{matrix.rust}} 17 | runs-on: ubuntu-latest 18 | strategy: 19 | fail-fast: false 20 | matrix: 21 | rust: [nightly, beta, stable, 1.36.0] 22 | timeout-minutes: 45 23 | steps: 24 | - uses: actions/checkout@v3 25 | - uses: dtolnay/rust-toolchain@master 26 | with: 27 | toolchain: ${{matrix.rust}} 28 | - run: cargo test 29 | 30 | miri: 31 | name: Miri 32 | runs-on: ubuntu-latest 33 | timeout-minutes: 45 34 | steps: 35 | - uses: actions/checkout@v3 36 | - uses: dtolnay/rust-toolchain@miri 37 | - run: cargo miri test 38 | env: 39 | MIRIFLAGS: -Zmiri-tag-raw-pointers 40 | 41 | clippy: 42 | name: Clippy 43 | runs-on: ubuntu-latest 44 | if: github.event_name != 'pull_request' 45 | timeout-minutes: 45 46 | steps: 47 | - uses: actions/checkout@v3 48 | - uses: dtolnay/rust-toolchain@clippy 49 | - run: cargo clippy --tests -- -Dclippy::all -Dclippy::pedantic 50 | 51 | outdated: 52 | name: Outdated 53 | runs-on: ubuntu-latest 54 | if: github.event_name != 'pull_request' 55 | timeout-minutes: 45 56 | steps: 57 | - uses: actions/checkout@v3 58 | - uses: dtolnay/install@cargo-outdated 59 | - run: cargo outdated --workspace --exit-code 1 60 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | /target 2 | **/*.rs.bk 3 | Cargo.lock 4 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "hackfn" 3 | version = "0.1.8" 4 | authors = ["David Tolnay "] 5 | description = "Fake implementation of `std::ops::Fn` for user-defined data types." 6 | documentation = "https://docs.rs/hackfn" 7 | edition = "2018" 8 | license = "MIT OR Apache-2.0" 9 | repository = "https://github.com/dtolnay/hackfn" 10 | rust-version = "1.36" 11 | 12 | [lib] 13 | proc-macro = true 14 | 15 | [dependencies] 16 | proc-macro2 = "1.0" 17 | quote = "1.0" 18 | syn = "1.0" 19 | 20 | [package.metadata.docs.rs] 21 | rustdoc-args = ["--cfg", "docs_rs_workaround"] 22 | targets = ["x86_64-unknown-linux-gnu"] 23 | -------------------------------------------------------------------------------- /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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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 | # \#\[hackfn\] 2 | 3 | [github](https://github.com/dtolnay/hackfn) 4 | [crates.io](https://crates.io/crates/hackfn) 5 | [docs.rs](https://docs.rs/hackfn) 6 | [build status](https://github.com/dtolnay/hackfn/actions?query=branch%3Amaster) 7 | 8 | Fake implementation of `std::ops::Fn` for user-defined data types. 9 | 10 | Place a `#[hackfn]` attribute on an impl block containing a single method to use 11 | that method as the implementation of the function call operator. 12 | 13 | ```toml 14 | [dependencies] 15 | hackfn = "0.1" 16 | ``` 17 | 18 | *Version requirement: \#\[hackfn\] supports rustc 1.31+* 19 | 20 | ## Limitations 21 | 22 | - The function must receive `&self`. Functions that receive `&mut self` or 23 | `self` are not supported. 24 | 25 | - The function may not have generic parameters or where-clause. 26 | 27 | - The `Self` type must implement `Sized`. 28 | 29 | ## Examples 30 | 31 | ```rust 32 | use hackfn::hackfn; 33 | 34 | /// Function object that adds some number to its input. 35 | struct Plus(u32); 36 | 37 | #[hackfn] 38 | impl Plus { 39 | fn call(&self, other: u32) -> u32 { 40 | self.0 + other 41 | } 42 | } 43 | 44 | fn main() { 45 | let plus_one = Plus(1); 46 | let sum = plus_one(2); 47 | assert_eq!(sum, 3); 48 | } 49 | ``` 50 | 51 | The next example is somewhat more elaborate: 52 | 53 | - Interior mutability can be used to approximate a `FnMut` impl. 54 | 55 | - Generic parameters and where-clause are permitted on the impl block (though 56 | not on the function). 57 | 58 | - The function may take any number of arguments. 59 | 60 | ```rust 61 | use hackfn::hackfn; 62 | 63 | use std::cell::Cell; 64 | use std::ops::Add; 65 | 66 | /// Function object that accumulates a pair of values per call. 67 | #[derive(Default)] 68 | struct AccumulatePairs { 69 | first: Cell, 70 | second: Cell, 71 | } 72 | 73 | #[hackfn] 74 | impl AccumulatePairs where T: Copy + Add { 75 | fn call(&self, first: T, second: T) { 76 | self.first.set(self.first.get() + first); 77 | self.second.set(self.second.get() + second); 78 | } 79 | } 80 | 81 | fn main() { 82 | let accumulate = AccumulatePairs::default(); 83 | accumulate(30, 1); 84 | accumulate(20, 2); 85 | accumulate(10, 3); 86 | assert_eq!(accumulate.first.get(), 60); 87 | assert_eq!(accumulate.second.get(), 6); 88 | } 89 | ``` 90 | 91 |
92 | 93 | #### License 94 | 95 | 96 | Licensed under either of Apache License, Version 97 | 2.0 or MIT license at your option. 98 | 99 | 100 |
101 | 102 | 103 | Unless you explicitly state otherwise, any contribution intentionally submitted 104 | for inclusion in this crate by you, as defined in the Apache-2.0 license, shall 105 | be dual licensed as above, without any additional terms or conditions. 106 | 107 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | //! [![github]](https://github.com/dtolnay/hackfn) [![crates-io]](https://crates.io/crates/hackfn) [![docs-rs]](https://docs.rs/hackfn) 2 | //! 3 | //! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github 4 | //! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust 5 | //! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs 6 | //! 7 | //!
8 | //! 9 | //! Fake implementation of `std::ops::Fn` for user-defined data types. 10 | //! 11 | //! Place a `#[hackfn]` attribute on an impl block containing a single method to 12 | //! use that method as the implementation of the function call operator. 13 | //! 14 | //! # Limitations 15 | //! 16 | //! - The function must receive `&self`. Functions that receive `&mut self` or 17 | //! `self` are not supported. 18 | //! 19 | //! - The function may not have generic parameters or where-clause. 20 | //! 21 | //! - The `Self` type must implement `Sized`. 22 | //! 23 | //! # Examples 24 | //! 25 | //! ``` 26 | //! use hackfn::hackfn; 27 | //! 28 | //! /// Function object that adds some number to its input. 29 | //! struct Plus(u32); 30 | //! 31 | //! #[hackfn] 32 | //! impl Plus { 33 | //! fn call(&self, other: u32) -> u32 { 34 | //! self.0 + other 35 | //! } 36 | //! } 37 | //! 38 | //! fn main() { 39 | //! let plus_one = Plus(1); 40 | //! let sum = plus_one(2); 41 | //! assert_eq!(sum, 3); 42 | //! } 43 | //! ``` 44 | //! 45 | //! The next example is somewhat more elaborate: 46 | //! 47 | //! - Interior mutability can be used to approximate a `FnMut` impl. 48 | //! 49 | //! - Generic parameters and where-clause are permitted on the impl block 50 | //! (though not on the function). 51 | //! 52 | //! - The function may take any number of arguments. 53 | //! 54 | //! ``` 55 | //! use hackfn::hackfn; 56 | //! 57 | //! use std::cell::Cell; 58 | //! use std::ops::Add; 59 | //! 60 | //! /// Function object that accumulates a pair of values per call. 61 | //! #[derive(Default)] 62 | //! struct AccumulatePairs { 63 | //! first: Cell, 64 | //! second: Cell, 65 | //! } 66 | //! 67 | //! #[hackfn] 68 | //! impl AccumulatePairs where T: Copy + Add { 69 | //! fn call(&self, first: T, second: T) { 70 | //! self.first.set(self.first.get() + first); 71 | //! self.second.set(self.second.get() + second); 72 | //! } 73 | //! } 74 | //! 75 | //! fn main() { 76 | //! let accumulate = AccumulatePairs::default(); 77 | //! accumulate(30, 1); 78 | //! accumulate(20, 2); 79 | //! accumulate(10, 3); 80 | //! assert_eq!(accumulate.first.get(), 60); 81 | //! assert_eq!(accumulate.second.get(), 6); 82 | //! } 83 | //! ``` 84 | 85 | #![cfg_attr(docs_rs_workaround, feature(proc_macro))] 86 | #![allow(clippy::needless_doctest_main)] 87 | 88 | extern crate proc_macro; 89 | 90 | use proc_macro::TokenStream; 91 | use proc_macro2::TokenStream as TokenStream2; 92 | use quote::quote; 93 | use syn::parse::{Nothing, Parse, ParseStream, Result}; 94 | use syn::{ 95 | braced, parenthesized, parse_macro_input, Attribute, Generics, Ident, Token, Type, Visibility, 96 | }; 97 | 98 | struct FnArg { 99 | ident: Ident, 100 | ty: Type, 101 | } 102 | 103 | impl Parse for FnArg { 104 | fn parse(input: ParseStream) -> Result { 105 | let ident = input.parse()?; 106 | input.parse::()?; 107 | let ty = input.parse()?; 108 | Ok(FnArg { ident, ty }) 109 | } 110 | } 111 | 112 | struct HackFn { 113 | impl_attrs: Vec, 114 | generics: Generics, 115 | self_ty: Type, 116 | fn_attrs: Vec, 117 | vis: Visibility, 118 | method: Ident, 119 | args: Vec, 120 | ret_ty: Option, 121 | body: TokenStream2, 122 | } 123 | 124 | impl Parse for HackFn { 125 | fn parse(input: ParseStream) -> Result { 126 | let impl_attrs = input.call(Attribute::parse_outer)?; 127 | input.parse::()?; 128 | let mut generics: Generics = input.parse()?; 129 | let self_ty: Type = input.parse()?; 130 | generics.where_clause = input.parse()?; 131 | 132 | let impl_block; 133 | braced!(impl_block in input); 134 | 135 | let fn_attrs = impl_block.call(Attribute::parse_outer)?; 136 | let vis: Visibility = impl_block.parse()?; 137 | impl_block.parse::()?; 138 | let method: Ident = impl_block.parse()?; 139 | 140 | let argument_list; 141 | parenthesized!(argument_list in impl_block); 142 | argument_list.parse::()?; 143 | argument_list.parse::()?; 144 | 145 | let mut args = Vec::new(); 146 | while !argument_list.is_empty() { 147 | argument_list.parse::()?; 148 | if argument_list.is_empty() { 149 | break; 150 | } 151 | args.push(argument_list.parse::()?); 152 | } 153 | 154 | let ret_ty = if impl_block.parse::]>>()?.is_some() { 155 | Some(impl_block.parse::()?) 156 | } else { 157 | None 158 | }; 159 | 160 | let body; 161 | braced!(body in impl_block); 162 | let body: TokenStream2 = body.parse()?; 163 | 164 | Ok(HackFn { 165 | impl_attrs, 166 | generics, 167 | self_ty, 168 | fn_attrs, 169 | vis, 170 | method, 171 | args, 172 | ret_ty, 173 | body, 174 | }) 175 | } 176 | } 177 | 178 | #[proc_macro_attribute] 179 | pub fn hackfn(args: TokenStream, input: TokenStream) -> TokenStream { 180 | parse_macro_input!(args as Nothing); 181 | 182 | let HackFn { 183 | impl_attrs, 184 | generics, 185 | self_ty, 186 | fn_attrs, 187 | vis, 188 | method, 189 | args, 190 | ret_ty, 191 | body, 192 | } = parse_macro_input!(input as HackFn); 193 | 194 | let impl_attrs = &impl_attrs; 195 | let where_clause = &generics.where_clause; 196 | let arg_names = args.iter().map(|fn_arg| &fn_arg.ident).collect::>(); 197 | let arg_types = args.iter().map(|fn_arg| &fn_arg.ty).collect::>(); 198 | let ret_ty = ret_ty.map(|ret| quote!(-> #ret)); 199 | 200 | let target = quote! { 201 | dyn ::std::ops::Fn(#(#arg_types),*) #ret_ty 202 | }; 203 | 204 | let expanded = quote! { 205 | #(#impl_attrs)* 206 | impl #generics #self_ty #where_clause { 207 | #(#fn_attrs)* 208 | #vis fn #method(&self #(, #arg_names: #arg_types)*) #ret_ty { 209 | #body 210 | } 211 | } 212 | 213 | #(#impl_attrs)* 214 | impl #generics ::std::ops::Deref for #self_ty #where_clause { 215 | type Target = #target; 216 | 217 | // This implementation assumes that a closure that captures a type T 218 | // by move has the same layout as T. 219 | #[allow(clippy::forget_non_drop, clippy::transmute_ptr_to_ptr)] 220 | fn deref(&self) -> &Self::Target { 221 | let __this = ::std::mem::MaybeUninit::::uninit(); 222 | let __closure = move |#(#arg_names : #arg_types),*| #ret_ty { 223 | Self::#method( 224 | unsafe { &*__this.as_ptr() } 225 | #(, #arg_names)* 226 | ) 227 | }; 228 | let __layout_of_closure = ::std::alloc::Layout::for_value(&__closure); 229 | fn __second<'__a, __T>(__first: &__T, __second: &'__a __T) -> &'__a __T { 230 | __second 231 | } 232 | let __ret = __second(&__closure, unsafe { &*(self as *const Self as *const _) }); 233 | ::std::mem::forget(__closure); 234 | assert_eq!(__layout_of_closure, ::std::alloc::Layout::new::()); 235 | unsafe { ::std::mem::transmute(__ret as &#target) } 236 | } 237 | } 238 | }; 239 | 240 | TokenStream::from(expanded) 241 | } 242 | -------------------------------------------------------------------------------- /tests/readme.rs: -------------------------------------------------------------------------------- 1 | mod first { 2 | use hackfn::hackfn; 3 | 4 | /// Function object that adds some number to its input. 5 | struct Plus(u32); 6 | 7 | #[hackfn] 8 | impl Plus { 9 | fn call(&self, other: u32) -> u32 { 10 | self.0 + other 11 | } 12 | } 13 | 14 | #[test] 15 | fn main() { 16 | let plus_one = Plus(1); 17 | let sum = plus_one(2); 18 | assert_eq!(sum, 3); 19 | } 20 | } 21 | 22 | mod second { 23 | use hackfn::hackfn; 24 | 25 | use std::cell::Cell; 26 | use std::ops::Add; 27 | 28 | /// Function object that accumulates a pair of values per call. 29 | #[derive(Default)] 30 | struct AccumulatePairs { 31 | first: Cell, 32 | second: Cell, 33 | } 34 | 35 | #[hackfn] 36 | impl AccumulatePairs 37 | where 38 | T: Copy + Add, 39 | { 40 | fn call(&self, first: T, second: T) { 41 | self.first.set(self.first.get() + first); 42 | self.second.set(self.second.get() + second); 43 | } 44 | } 45 | 46 | #[test] 47 | fn main() { 48 | let accumulate = AccumulatePairs::::default(); 49 | accumulate(30, 1); 50 | accumulate(20, 2); 51 | accumulate(10, 3); 52 | assert_eq!(accumulate.first.get(), 60); 53 | assert_eq!(accumulate.second.get(), 6); 54 | } 55 | } 56 | --------------------------------------------------------------------------------