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Diffstat (limited to 'third_party/rust/rustversion/src/lib.rs')
| -rw-r--r-- | third_party/rust/rustversion/src/lib.rs | 247 |
1 files changed, 247 insertions, 0 deletions
diff --git a/third_party/rust/rustversion/src/lib.rs b/third_party/rust/rustversion/src/lib.rs new file mode 100644 index 0000000000..2e8f1b94d9 --- /dev/null +++ b/third_party/rust/rustversion/src/lib.rs @@ -0,0 +1,247 @@ +//! [![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>#[rustversion::stable]</code></b> +//! —<br> +//! True on any stable compiler. +//! </p> +//! +//! - <p style="margin-left:50px;text-indent:-50px"> +//! <b><code>#[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>#[rustversion::beta]</code></b> +//! —<br> +//! True on any beta compiler. +//! </p> +//! +//! - <p style="margin-left:50px;text-indent:-50px"> +//! <b><code>#[rustversion::nightly]</code></b> +//! —<br> +//! True on any nightly compiler or dev build. +//! </p> +//! +//! - <p style="margin-left:50px;text-indent:-50px"> +//! <b><code>#[rustversion::nightly(2019-01-01)]</code></b> +//! —<br> +//! True on exactly one nightly. +//! </p> +//! +//! - <p style="margin-left:50px;text-indent:-50px"> +//! <b><code>#[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>#[rustversion::since(2019-01-01)]</code></b> +//! —<br> +//! True on that nightly and all newer ones. +//! </p> +//! +//! - <p style="margin-left:50px;text-indent:-50px"> +//! <b><code>#[rustversion::before(</code></b><i>version or date</i><b><code>)]</code></b> +//! —<br> +//! Negative of <i>#[rustversion::since(...)]</i>. +//! </p> +//! +//! - <p style="margin-left:50px;text-indent:-50px"> +//! <b><code>#[rustversion::not(</code></b><i>selector</i><b><code>)]</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>#[rustversion::any(</code></b><i>selectors...</i><b><code>)]</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>#[rustversion::all(</code></b><i>selectors...</i><b><code>)]</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>#[rustversion::attr(</code></b><i>selector</i><b><code>, </code></b><i>attribute</i><b><code>)]</code></b> +//! —<br> +//! For conditional inclusion of attributes; analogous to +//! <code>cfg_attr</code>. +//! </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 +//! } +//! ``` +//! +//! <br> + +#![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; + +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) +} |