diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-30 18:31:44 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-30 18:31:44 +0000 |
commit | c23a457e72abe608715ac76f076f47dc42af07a5 (patch) | |
tree | 2772049aaf84b5c9d0ed12ec8d86812f7a7904b6 /library/core/src/macros/mod.rs | |
parent | Releasing progress-linux version 1.73.0+dfsg1-1~progress7.99u1. (diff) | |
download | rustc-c23a457e72abe608715ac76f076f47dc42af07a5.tar.xz rustc-c23a457e72abe608715ac76f076f47dc42af07a5.zip |
Merging upstream version 1.74.1+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'library/core/src/macros/mod.rs')
-rw-r--r-- | library/core/src/macros/mod.rs | 93 |
1 files changed, 91 insertions, 2 deletions
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs index 14cc523b0..123661b35 100644 --- a/library/core/src/macros/mod.rs +++ b/library/core/src/macros/mod.rs @@ -168,6 +168,94 @@ pub macro assert_matches { }, } +/// A macro for defining `#[cfg]` match-like statements. +/// +/// It is similar to the `if/elif` C preprocessor macro by allowing definition of a cascade of +/// `#[cfg]` cases, emitting the implementation which matches first. +/// +/// This allows you to conveniently provide a long list `#[cfg]`'d blocks of code +/// without having to rewrite each clause multiple times. +/// +/// Trailing `_` wildcard match arms are **optional** and they indicate a fallback branch when +/// all previous declarations do not evaluate to true. +/// +/// # Example +/// +/// ``` +/// #![feature(cfg_match)] +/// +/// cfg_match! { +/// cfg(unix) => { +/// fn foo() { /* unix specific functionality */ } +/// } +/// cfg(target_pointer_width = "32") => { +/// fn foo() { /* non-unix, 32-bit functionality */ } +/// } +/// _ => { +/// fn foo() { /* fallback implementation */ } +/// } +/// } +/// ``` +#[unstable(feature = "cfg_match", issue = "115585")] +#[rustc_diagnostic_item = "cfg_match"] +pub macro cfg_match { + // with a final wildcard + ( + $(cfg($initial_meta:meta) => { $($initial_tokens:item)* })+ + _ => { $($extra_tokens:item)* } + ) => { + cfg_match! { + @__items (); + $((($initial_meta) ($($initial_tokens)*)),)+ + (() ($($extra_tokens)*)), + } + }, + + // without a final wildcard + ( + $(cfg($extra_meta:meta) => { $($extra_tokens:item)* })* + ) => { + cfg_match! { + @__items (); + $((($extra_meta) ($($extra_tokens)*)),)* + } + }, + + // Internal and recursive macro to emit all the items + // + // Collects all the previous cfgs in a list at the beginning, so they can be + // negated. After the semicolon is all the remaining items. + (@__items ($($_:meta,)*);) => {}, + ( + @__items ($($no:meta,)*); + (($($yes:meta)?) ($($tokens:item)*)), + $($rest:tt,)* + ) => { + // Emit all items within one block, applying an appropriate #[cfg]. The + // #[cfg] will require all `$yes` matchers specified and must also negate + // all previous matchers. + #[cfg(all( + $($yes,)? + not(any($($no),*)) + ))] + cfg_match! { @__identity $($tokens)* } + + // Recurse to emit all other items in `$rest`, and when we do so add all + // our `$yes` matchers to the list of `$no` matchers as future emissions + // will have to negate everything we just matched as well. + cfg_match! { + @__items ($($no,)* $($yes,)?); + $($rest,)* + } + }, + + // Internal macro to make __apply work out right for different match types, + // because of how macros match/expand stuff. + (@__identity $($tokens:item)*) => { + $($tokens)* + } +} + /// Asserts that a boolean expression is `true` at runtime. /// /// This will invoke the [`panic!`] macro if the provided expression cannot be @@ -849,7 +937,8 @@ pub(crate) mod builtin { /// assert_eq!(display, debug); /// ``` /// - /// For more information, see the documentation in [`std::fmt`]. + /// See [the formatting documentation in `std::fmt`](../std/fmt/index.html) + /// for details of the macro argument syntax, and further information. /// /// [`Display`]: crate::fmt::Display /// [`Debug`]: crate::fmt::Debug @@ -1043,7 +1132,7 @@ pub(crate) mod builtin { /// expression of type `&'static str` which represents all of the literals /// concatenated left-to-right. /// - /// Integer and floating point literals are stringified in order to be + /// Integer and floating point literals are [stringified](core::stringify) in order to be /// concatenated. /// /// # Examples |