Macro std::assert_matches::debug_assert_matches

pub macro debug_assert_matches($($arg:tt)*) {
    ...
}

🔬This is a nightly-only experimental API. (assert_matches #82775)

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

#![feature(assert_matches)]

use std::assert_matches::debug_assert_matches;

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!(c, Ok(x) | Err(x) if x.len() < 100);