<ins> // 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. //! //! # Example //! //! ``` //! #[macro_use] extern crate enum_primitive; //! extern crate num_traits; //! use num_traits::FromPrimitive; //! //! enum_from_primitive! { //! #[derive(Debug, PartialEq)] //! enum FooBar { //!     Foo = 17, //!     Bar = 42, //!     Baz, //! } //! } //! //! 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(43), Some(FooBar::Baz)); //!     assert_eq!(FooBar::from_i32(91), None); //! } //! ``` pub mod num_traits { pub trait FromPrimitive: Sized { fn from_i64(n: i64) -> Option<Self>; fn from_u64(n: u64) -> Option<Self>; } } pub use std::option::Option; pub use num_traits::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, unused)] fn $meth(n: $ty) -> $crate::Option<Self> { $( if n == $name::$variant as $ty { $crate::Option::Some($name::$variant) } else )* { $crate::Option::None } } }; } /// Helper macro for internal use by `enum_from_primitive!`. #[macro_export] #[macro_use(enum_from_primitive_impl_ty)] macro_rules! enum_from_primitive_impl { ($name:ident, $( $variant:ident )*) => { impl $crate::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, $( $( #[$variant_two_attr:meta] )* $variant_two:ident ),+ )* } ) => { $( #[$enum_attr] )* enum $name { $( $( #[$variant_attr] )* $variant ),+ $( = $discriminator, $( $( #[$variant_two_attr] )* $variant_two ),+ )* } enum_from_primitive_impl! { $name, $( $variant )+ $( $( $variant_two )+ )* } }; ( $( #[$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, $( $( #[$variant_two_attr:meta] )* $variant_two:ident ),+ )*, } ) => { $( #[$enum_attr] )* enum $name { $( $( #[$variant_attr] )* $variant ),+ $( = $discriminator, $( $( #[$variant_two_attr] )* $variant_two ),+ )*, } enum_from_primitive_impl! { $name, $( $variant )+ $( $( $variant_two )+ )* } }; ( $( #[$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] )* pub enum $name:ident { $( $( #[$variant_attr:meta] )* $variant:ident ),+ $( = $discriminator:expr, $( $( #[$variant_two_attr:meta] )* $variant_two:ident ),+ )* } ) => { $( #[$enum_attr] )* pub enum $name { $( $( #[$variant_attr] )* $variant ),+ $( = $discriminator, $( $( #[$variant_two_attr] )* $variant_two ),+ )* } enum_from_primitive_impl! { $name, $( $variant )+ $( $( $variant_two )+ )* } }; ( $( #[$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, $( $( #[$variant_two_attr:meta] )* $variant_two:ident ),+ )*, } ) => { $( #[$enum_attr] )* pub enum $name { $( $( #[$variant_attr] )* $variant ),+ $( = $discriminator, $( $( #[$variant_two_attr] )* $variant_two ),+ )*, } enum_from_primitive_impl! { $name, $( $variant )+ $( $( $variant_two )+ )* } }; ( $( #[$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 )+ )+ } }; } </ins>