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// Copyright (c) 2015 Anders Kaseorg <andersk@mit.edu> // Permission is hereby granted, free of charge, to any person obtaining // a copy of this software and associated documentation files (the // “Software”), to deal in the Software without restriction, including // without limitation the rights to use, copy, modify, merge, publish, // distribute, sublicense, and/or sell copies of the Software, and to // permit persons to whom the Software is furnished to do so, subject to // the following conditions: // The above copyright notice and this permission notice shall be // included in all copies or substantial portions of the Software. // THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. // IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY // CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, // TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE // SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. //! This crate exports a macro `enum_from_primitive!` that wraps an //! `enum` declaration and automatically adds an implementation of //! `num::FromPrimitive` (reexported here), to allow conversion from //! primitive integers to the enum. It therefore provides an //! alternative to the built-in `#[derive(FromPrimitive)]`, which //! requires the unstable `std::num::FromPrimitive` and is disabled in //! Rust 1.0. //! //! The current implementation requires all variants of the num to //! have an explicit discriminator value. This restriction may be //! relaxed in future versions. //! //! # Example //! //! ``` //! #[macro_use] extern crate enum_primitive; //! extern crate num; //! use num::FromPrimitive; //! //! enum_from_primitive! { //! #[derive(Debug, PartialEq)] //! enum FooBar { //! Foo = 17, //! Bar = 42, //! } //! } //! //! fn main() { //! assert_eq!(FooBar::from_i32(17), Some(FooBar::Foo)); //! assert_eq!(FooBar::from_i32(42), Some(FooBar::Bar)); //! assert_eq!(FooBar::from_i32(91), None); //! } //! ``` extern crate num; pub use num::FromPrimitive; /// Helper macro for internal use by `enum_from_primitive!`. #[macro_export] macro_rules! enum_from_primitive_impl_ty { ($meth:ident, $ty:ty, $name:ident, $( $variant:ident ),*) => { #[allow(non_upper_case_globals)] fn $meth(n: $ty) -> ::std::option::Option<Self> { $( const $variant: $ty = $name::$variant as $ty; )* match n { $( $variant => ::std::option::Option::Some($name::$variant), )* _ => ::std::option::Option::None, } } } } /// Helper macro for internal use by `enum_from_primitive!`. #[macro_export] #[macro_use(enum_from_primitive_impl_ty)] macro_rules! enum_from_primitive_impl { ($name:ident, $( $variant:ident ),*) => { impl ::num::FromPrimitive for $name { enum_from_primitive_impl_ty! { from_i64, i64, $name, $( $variant ),* } enum_from_primitive_impl_ty! { from_u64, u64, $name, $( $variant ),* } } } } /// Wrap this macro around an `enum` declaration to get an /// automatically generated implementation of `num::FromPrimitive`. #[macro_export] #[macro_use(enum_from_primitive_impl)] macro_rules! enum_from_primitive { ( $( #[$enum_attr:meta] )* enum $name:ident { $( $( #[$variant_attr:meta] )* $variant:ident = $discriminator:expr ),* } ) => { $( #[$enum_attr] )* enum $name { $( $( #[$variant_attr] )* $variant = $discriminator ),* } enum_from_primitive_impl! { $name, $($variant),* } }; ( $( #[$enum_attr:meta] )* enum $name:ident { $( $( #[$variant_attr:meta] )* $variant:ident = $discriminator:expr ),*, } ) => { enum_from_primitive! { $( #[$enum_attr] )* enum $name { $( $( #[$variant_attr] )* $variant = $discriminator ),* } } }; ( $( #[$enum_attr:meta] )* pub enum $name:ident { $( $( #[$variant_attr:meta] )* $variant:ident = $discriminator:expr ),* } ) => { $( #[$enum_attr] )* pub enum $name { $( $( #[$variant_attr] )* $variant = $discriminator ),* } enum_from_primitive_impl! { $name, $( $variant ),* } }; ( $( #[$enum_attr:meta] )* pub enum $name:ident { $( $( #[$variant_attr:meta] )* $variant:ident = $discriminator:expr ),*, } ) => { enum_from_primitive! { $( #[$enum_attr] )* pub enum $name { $( $( #[$variant_attr] )* $variant = $discriminator ),* } } }; }