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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.
    //!
    //! # 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);
    //! }
    //! ```

    extern crate num_traits;

    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 )+ )+ }
        };
    }

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