io-enum 0.2.4

#[derive(Read, Write, Seek, BufRead)] for enums.
Documentation 
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//! \#\[derive(Read, Write, Seek, BufRead)\] for enums.
//!
//! # Examples
//!
//! ```rust
//! use io_enum::*;
//! use std::{
//!     fs::File,
//!     io::{self, Write},
//!     path::Path,
//! };
//!
//! #[derive(Read, Write, Seek, BufRead)]
//! enum Either<A, B> {
//!     A(A),
//!     B(B),
//! }
//!
//! fn foo(path: Option<&Path>) -> impl Write {
//!     if let Some(path) = path {
//!         Either::A(File::open(path).unwrap())
//!     } else {
//!         Either::B(io::stdout())
//!     }
//! }
//! ```
//!
//! See [auto_enums](https://github.com/taiki-e/auto_enums) crate for how to automate patterns like this.
//!
//! # Supported traits
//!
//! * [`Read`](https://doc.rust-lang.org/std/io/trait.Read.html) - [generated code](https://github.com/taiki-e/io-enum/blob/master/doc/read.md)
//! * [`BufRead`](https://doc.rust-lang.org/std/io/trait.BufRead.html) - [generated code](https://github.com/taiki-e/io-enum/blob/master/doc/buf_read.md)
//! * [`Write`](https://doc.rust-lang.org/std/io/trait.Write.html) - [generated code](https://github.com/taiki-e/io-enum/blob/master/doc/write.md)
//! * [`Seek`](https://doc.rust-lang.org/std/io/trait.Seek.html) - [generated code](https://github.com/taiki-e/io-enum/blob/master/doc/seek.md)

#![doc(html_root_url = "https://docs.rs/io-enum/0.2.4")]
#![doc(test(
    no_crate_inject,
    attr(deny(warnings, rust_2018_idioms, single_use_lifetimes), allow(dead_code))
))]
#![forbid(unsafe_code)]
#![warn(future_incompatible, rust_2018_idioms, single_use_lifetimes, unreachable_pub)]
#![warn(clippy::all, clippy::default_trait_access)]
// mem::take, #[non_exhaustive], and Option::{as_deref, as_deref_mut} require Rust 1.40,
// matches! requires Rust 1.42, str::{strip_prefix, strip_suffix} requires Rust 1.45
#![allow(
    clippy::mem_replace_with_default,
    clippy::manual_non_exhaustive,
    clippy::option_as_ref_deref,
    clippy::match_like_matches_macro,
    clippy::manual_strip
)]

// older compilers require explicit `extern crate`.
#[allow(unused_extern_crates)]
extern crate proc_macro;

use derive_utils::{derive_trait, quick_derive};
use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, parse_quote};

#[proc_macro_derive(Read)]
pub fn derive_read(input: TokenStream) -> TokenStream {
    #[cfg(not(stable_1_36))]
    let vectored = quote!();
    #[cfg(stable_1_36)]
    let vectored = quote! {
        #[inline]
        fn read_vectored(
            &mut self, bufs: &mut [::std::io::IoSliceMut<'_>],
        ) -> ::std::io::Result<usize>;
    };

    // TODO: When `read_initializer` stabilized, add `initializer` conditionally.

    derive_trait(&parse_macro_input!(input), parse_quote!(::std::io::Read), None, parse_quote! {
        trait Read {
            #[inline]
            fn read(&mut self, buf: &mut [u8]) -> ::std::io::Result<usize>;
            #[inline]
            fn read_to_end(&mut self, buf: &mut ::std::vec::Vec<u8>) -> ::std::io::Result<usize>;
            #[inline]
            fn read_to_string(
                &mut self,
                buf: &mut ::std::string::String,
            ) -> ::std::io::Result<usize>;
            #[inline]
            fn read_exact(&mut self, buf: &mut [u8]) -> ::std::io::Result<()>;
            #vectored
        }
    })
    .into()
}

#[proc_macro_derive(BufRead)]
pub fn derive_buf_read(input: TokenStream) -> TokenStream {
    quick_derive! {
        input,
        ::std::io::BufRead,
        trait BufRead {
            #[inline]
            fn fill_buf(&mut self) -> ::std::io::Result<&[u8]>;
            #[inline]
            fn consume(&mut self, amt: usize);
            #[inline]
            fn read_until(
                &mut self, byte: u8, buf: &mut ::std::vec::Vec<u8>,
            ) -> ::std::io::Result<usize>;
            #[inline]
            fn read_line(&mut self, buf: &mut ::std::string::String) -> ::std::io::Result<usize>;
        }
    }
}

#[proc_macro_derive(Write)]
pub fn derive_write(input: TokenStream) -> TokenStream {
    #[cfg(not(stable_1_36))]
    let vectored = quote!();
    #[cfg(stable_1_36)]
    let vectored = quote! {
        #[inline]
        fn write_vectored(&mut self, bufs: &[::std::io::IoSlice<'_>]) -> ::std::io::Result<usize>;
    };

    derive_trait(&parse_macro_input!(input), parse_quote!(::std::io::Write), None, parse_quote! {
        trait Write {
            #[inline]
            fn write(&mut self, buf: &[u8]) -> ::std::io::Result<usize>;
            #[inline]
            fn flush(&mut self) -> ::std::io::Result<()>;
            #[inline]
            fn write_all(&mut self, buf: &[u8]) -> ::std::io::Result<()>;
            #[inline]
            fn write_fmt(&mut self, fmt: ::std::fmt::Arguments<'_>) -> ::std::io::Result<()>;
            #vectored
        }
    })
    .into()
}

#[proc_macro_derive(Seek)]
pub fn derive_seek(input: TokenStream) -> TokenStream {
    quick_derive! {
        input,
        ::std::io::Seek,
        trait Seek {
            #[inline]
            fn seek(&mut self, pos: ::std::io::SeekFrom) -> ::std::io::Result<u64>;
        }
    }
}