rustversion/

lib.rs

//! [![github]](https://github.com/dtolnay/rustversion) [![crates-io]](https://crates.io/crates/rustversion) [![docs-rs]](https://docs.rs/rustversion)
//!
//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
//!
//! <br>
//!
//! This crate provides macros for conditional compilation according to rustc
//! compiler version, analogous to [`#[cfg(...)]`][cfg] and
//! [`#[cfg_attr(...)]`][cfg_attr].
//!
//! [cfg]: https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute
//! [cfg_attr]: https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute
//!
//! <br>
//!
//! # Selectors
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::stable]</code></b>
//!   —<br>
//!   True on any stable compiler.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::stable(1.34)]</code></b>
//!   —<br>
//!   True on exactly the specified stable compiler.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::beta]</code></b>
//!   —<br>
//!   True on any beta compiler.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::nightly]</code></b>
//!   —<br>
//!   True on any nightly compiler or dev build.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::nightly(2025-01-01)]</code></b>
//!   —<br>
//!   True on exactly one nightly.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::since(1.34)]</code></b>
//!   —<br>
//!   True on that stable release and any later compiler, including beta and
//!   nightly.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::since(2025-01-01)]</code></b>
//!   —<br>
//!   True on that nightly and all newer ones.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::before(</code></b><i>version or date</i><b><code style="display:inline">)]</code></b>
//!   —<br>
//!   Negative of <i>#[rustversion::since(...)]</i>.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::not(</code></b><i>selector</i><b><code style="display:inline">)]</code></b>
//!   —<br>
//!   Negative of any selector; for example <i>#[rustversion::not(nightly)]</i>.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::any(</code></b><i>selectors...</i><b><code style="display:inline">)]</code></b>
//!   —<br>
//!   True if any of the comma-separated selectors is true; for example
//!   <i>#[rustversion::any(stable, beta)]</i>.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::all(</code></b><i>selectors...</i><b><code style="display:inline">)]</code></b>
//!   —<br>
//!   True if all of the comma-separated selectors are true; for example
//!   <i>#[rustversion::all(since(1.31), before(1.34))]</i>.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">#[rustversion::attr(</code></b><i>selector</i><b><code style="display:inline">, </code></b><i>attribute</i><b><code style="display:inline">)]</code></b>
//!   —<br>
//!   For conditional inclusion of attributes; analogous to
//!   <code style="display:inline">cfg_attr</code>.
//!   </p>
//!
//! - <p style="margin-left:50px;text-indent:-50px">
//!   <b><code style="display:inline">rustversion::cfg!(</code></b><i>selector</i><b><code style="display:inline">)</code></b>
//!   —<br>
//!   An expression form of any of the above attributes; for example
//!   <i>if rustversion::cfg!(any(stable, beta)) { ... }</i>.
//!   </p>
//!
//! <br>
//!
//! # Use cases
//!
//! Providing additional trait impls as types are stabilized in the standard library
//! without breaking compatibility with older compilers; in this case Pin\<P\>
//! stabilized in [Rust 1.33][pin]:
//!
//! [pin]: https://blog.rust-lang.org/2019/02/28/Rust-1.33.0.html#pinning
//!
//! ```
//! # trait MyTrait {}
//! #
//! #[rustversion::since(1.33)]
//! use std::pin::Pin;
//!
//! #[rustversion::since(1.33)]
//! impl<P: MyTrait> MyTrait for Pin<P> {
//!     /* ... */
//! }
//! ```
//!
//! Similar but for language features; the ability to control alignment greater than
//! 1 of packed structs was stabilized in [Rust 1.33][packed].
//!
//! [packed]: https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-1330-2019-02-28
//!
//! ```
//! #[rustversion::attr(before(1.33), repr(packed))]
//! #[rustversion::attr(since(1.33), repr(packed(2)))]
//! struct Six(i16, i32);
//!
//! fn main() {
//!     println!("{}", std::mem::align_of::<Six>());
//! }
//! ```
//!
//! Augmenting code with `const` as const impls are stabilized in the standard
//! library. This use of `const` as an attribute is recognized as a special case
//! by the rustversion::attr macro.
//!
//! ```
//! use std::time::Duration;
//!
//! #[rustversion::attr(since(1.32), const)]
//! fn duration_as_days(dur: Duration) -> u64 {
//!     dur.as_secs() / 60 / 60 / 24
//! }
//! ```
//!
//! Emitting Cargo cfg directives from a build script. Note that this requires
//! listing `rustversion` under `[build-dependencies]` in Cargo.toml, not
//! `[dependencies]`.
//!
//! ```
//! // build.rs
//!
//! fn main() {
//!     if rustversion::cfg!(since(1.36)) {
//!         println!("cargo:rustc-cfg=no_std");
//!     }
//! }
//! ```
//!
//! ```
//! // src/lib.rs
//!
//! #![cfg_attr(no_std, no_std)]
//!
//! #[cfg(no_std)]
//! extern crate alloc;
//! ```
//!
//! <br>

#![doc(html_root_url = "https://docs.rs/rustversion/1.0.20")]
#![allow(
    clippy::cast_lossless,
    clippy::cast_possible_truncation,
    clippy::derive_partial_eq_without_eq,
    clippy::doc_markdown,
    clippy::enum_glob_use,
    clippy::from_iter_instead_of_collect,
    // https://github.com/rust-lang/rust-clippy/issues/8539
    clippy::iter_with_drain,
    clippy::module_name_repetitions,
    clippy::must_use_candidate,
    clippy::needless_doctest_main,
    clippy::needless_pass_by_value,
    clippy::redundant_else,
    clippy::toplevel_ref_arg,
    clippy::unreadable_literal
)]

extern crate proc_macro;

mod attr;
mod bound;
mod constfn;
mod date;
mod error;
mod expand;
mod expr;
mod iter;
mod release;
mod time;
mod token;
mod version;

use crate::error::Error;
use crate::version::Version;
use proc_macro::TokenStream;

#[cfg(not(host_os = "windows"))]
const RUSTVERSION: Version = include!(concat!(env!("OUT_DIR"), "/version.expr"));

#[cfg(host_os = "windows")]
const RUSTVERSION: Version = include!(concat!(env!("OUT_DIR"), "\\version.expr"));

#[proc_macro_attribute]
pub fn stable(args: TokenStream, input: TokenStream) -> TokenStream {
    expand::cfg("stable", args, input)
}

#[proc_macro_attribute]
pub fn beta(args: TokenStream, input: TokenStream) -> TokenStream {
    expand::cfg("beta", args, input)
}

#[proc_macro_attribute]
pub fn nightly(args: TokenStream, input: TokenStream) -> TokenStream {
    expand::cfg("nightly", args, input)
}

#[proc_macro_attribute]
pub fn since(args: TokenStream, input: TokenStream) -> TokenStream {
    expand::cfg("since", args, input)
}

#[proc_macro_attribute]
pub fn before(args: TokenStream, input: TokenStream) -> TokenStream {
    expand::cfg("before", args, input)
}

#[proc_macro_attribute]
pub fn not(args: TokenStream, input: TokenStream) -> TokenStream {
    expand::cfg("not", args, input)
}

#[proc_macro_attribute]
pub fn any(args: TokenStream, input: TokenStream) -> TokenStream {
    expand::cfg("any", args, input)
}

#[proc_macro_attribute]
pub fn all(args: TokenStream, input: TokenStream) -> TokenStream {
    expand::cfg("all", args, input)
}

#[proc_macro_attribute]
pub fn attr(args: TokenStream, input: TokenStream) -> TokenStream {
    attr::parse(args)
        .and_then(|args| expand::try_attr(args, input))
        .unwrap_or_else(Error::into_compile_error)
}

#[cfg(not(cfg_macro_not_allowed))]
#[proc_macro]
pub fn cfg(input: TokenStream) -> TokenStream {
    use proc_macro::{Ident, Span, TokenTree};
    (|| {
        let ref mut args = iter::new(input);
        let expr = expr::parse(args)?;
        token::parse_end(args)?;
        let boolean = expr.eval(RUSTVERSION);
        let ident = Ident::new(&boolean.to_string(), Span::call_site());
        Ok(TokenStream::from(TokenTree::Ident(ident)))
    })()
    .unwrap_or_else(Error::into_compile_error)
}