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Add debug_assert_matches macro.
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m-ou-se committed Mar 4, 2021
1 parent cfce60e commit 0a8e401
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Showing 2 changed files with 36 additions and 2 deletions.
34 changes: 34 additions & 0 deletions library/core/src/macros/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -260,6 +260,40 @@ macro_rules! debug_assert_ne {
($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert_ne!($($arg)*); })
}

/// Asserts that an expression matches any of the given patterns.
///
/// Like in a `match` expression, the pattern can be optionally followed by `if`
/// and a guard expression that has access to names bound by the pattern.
///
/// On panic, this macro will print the value of the expression with its
/// debug representation.
///
/// Unlike [`assert_matches!`], `debug_assert_matches!` statements are only
/// enabled in non optimized builds by default. An optimized build will not
/// execute `debug_assert_matches!` statements unless `-C debug-assertions` is
/// passed to the compiler. This makes `debug_assert_matches!` useful for
/// checks that are too expensive to be present in a release build but may be
/// helpful during development. The result of expanding `debug_assert_matches!`
/// is always type checked.
///
/// # Examples
///
/// ```
/// let a = 1u32.checked_add(2);
/// let b = 1u32.checked_sub(2);
/// debug_assert_matches!(a, Some(_));
/// debug_assert_matches!(b, None);
///
/// let c = Ok("abc".to_string());
/// debug_assert_matches!(a, Ok(x) | Err(x) if x.len() < 100);
/// ```
#[macro_export]
#[unstable(feature = "assert_matches", issue = "none")]
#[allow_internal_unstable(assert_matches)]
macro_rules! debug_assert_matches {
($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert_matches!($($arg)*); })
}

/// Returns whether the given expression matches any of the given patterns.
///
/// Like in a `match` expression, the pattern can be optionally followed by `if`
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4 changes: 2 additions & 2 deletions library/std/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -551,8 +551,8 @@ pub use std_detect::detect;
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated, deprecated_in_future)]
pub use core::{
assert_eq, assert_matches, assert_ne, debug_assert, debug_assert_eq, debug_assert_ne, matches,
r#try, todo, unimplemented, unreachable, write, writeln,
assert_eq, assert_matches, assert_ne, debug_assert, debug_assert_eq, debug_assert_matches,
debug_assert_ne, matches, r#try, todo, unimplemented, unreachable, write, writeln,
};

// Re-export built-in macros defined through libcore.
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