static_assert.rs

 1// SPDX-License-Identifier: GPL-2.0
 2
 3//! Static assert.
 4
 5/// Static assert (i.e. compile-time assert).
 6///
 7/// Similar to C11 [`_Static_assert`] and C++11 [`static_assert`].
 8///
 9/// An optional panic message can be supplied after the expression.
10/// Currently only a string literal without formatting is supported
11/// due to constness limitations of the [`assert!`] macro.
12///
13/// The feature may be added to Rust in the future: see [RFC 2790].
14///
15/// [`_Static_assert`]: https://en.cppreference.com/w/c/language/_Static_assert
16/// [`static_assert`]: https://en.cppreference.com/w/cpp/language/static_assert
17/// [RFC 2790]: https://github.com/rust-lang/rfcs/issues/2790
18///
19/// # Examples
20///
21/// ```
22/// static_assert!(42 > 24);
23/// static_assert!(core::mem::size_of::<u8>() == 1);
24///
25/// const X: &[u8] = b"bar";
26/// static_assert!(X[1] == b'a');
27///
28/// const fn f(x: i32) -> i32 {
29///     x + 2
30/// }
31/// static_assert!(f(40) == 42);
32/// static_assert!(f(40) == 42, "f(x) must add 2 to the given input.");
33/// ```
34#[macro_export]
35macro_rules! static_assert {
36    ($condition:expr $(,$arg:literal)?) => {
37        const _: () = ::core::assert!($condition $(,$arg)?);
38    };
39}