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    // Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
    // Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
    // Ana Hobden (@hoverbear) <operator@hoverbear.org>
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.
    //
    // This work was derived from Structopt (https://github.com/TeXitoi/structopt)
    // commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
    // MIT/Apache 2.0 license.

    #![doc(html_logo_url = "https://raw.githubusercontent.com/clap-rs/clap/master/assets/clap.png")]
    #![doc = include_str!("../README.md")]
    #![forbid(unsafe_code)]

    extern crate proc_macro;

    use proc_macro::TokenStream;
    use proc_macro_error::proc_macro_error;
    use syn::{parse_macro_input, DeriveInput};

    mod attr;
    mod derives;
    mod dummies;
    mod item;
    mod utils;

    /// Generates the `ValueEnum` impl.
    #[proc_macro_derive(ValueEnum, attributes(clap, value))]
    #[proc_macro_error]
    pub fn value_enum(input: TokenStream) -> TokenStream {
        let input: DeriveInput = parse_macro_input!(input);
        derives::derive_value_enum(&input).into()
    }

    /// Generates the `Parser` implementation.
    ///
    /// This is far less verbose than defining the `clap::Command` struct manually,
    /// receiving an instance of `clap::ArgMatches` from conducting parsing, and then
    /// implementing a conversion code to instantiate an instance of the user
    /// context struct.
    #[proc_macro_derive(Parser, attributes(clap, structopt, command, arg, group))]
    #[proc_macro_error]
    pub fn parser(input: TokenStream) -> TokenStream {
        let input: DeriveInput = parse_macro_input!(input);
        derives::derive_parser(&input).into()
    }

    /// Generates the `Subcommand` impl.
    #[proc_macro_derive(Subcommand, attributes(clap, command, arg, group))]
    #[proc_macro_error]
    pub fn subcommand(input: TokenStream) -> TokenStream {
        let input: DeriveInput = parse_macro_input!(input);
        derives::derive_subcommand(&input).into()
    }

    /// Generates the `Args` impl.
    #[proc_macro_derive(Args, attributes(clap, command, arg, group))]
    #[proc_macro_error]
    pub fn args(input: TokenStream) -> TokenStream {
        let input: DeriveInput = parse_macro_input!(input);
        derives::derive_args(&input).into()
    }