libkernel: add static_assert! macro

rust/kernel/lib.rs

@@ -40,6 +40,7 @@ pub mod module_param;
 pub mod prelude;
 pub mod printk;
 pub mod random;
+mod static_assert;
 
 #[cfg(CONFIG_SYSCTL)]
 pub mod sysctl;

rust/kernel/prelude.rs

@@ -15,4 +15,4 @@ pub use alloc::{borrow::ToOwned, string::String};
 
 pub use module::module;
 
-pub use super::{println, KernelModule, KernelResult};
+pub use super::{println, static_assert, KernelModule, KernelResult};

rust/kernel/static_assert.rs

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Static assert.
+
+/// Static assert (i.e. compile-time assert).
+///
+/// Similar to C11 [`_Static_assert`] and C++11 [`static_assert`].
+///
+/// The feature may be added to Rust in the future: see [RFC 2790].
+///
+/// [`_Static_assert`]: https://en.cppreference.com/w/c/language/_Static_assert
+/// [`static_assert`]: https://en.cppreference.com/w/cpp/language/static_assert
+/// [RFC 2790]: https://github.com/rust-lang/rfcs/issues/2790
+///
+/// # Examples
+///
+/// ```
+/// static_assert!(42 > 24);
+/// static_assert!(core::mem::size_of::<u8>() == 1);
+///
+/// const X: &[u8] = b"bar";
+/// static_assert!(X[1] == 'a' as u8);
+///
+/// const fn f(x: i32) -> i32 {
+///    x + 2
+/// }
+/// static_assert!(f(40) == 42);
+/// ```
+#[macro_export]
+macro_rules! static_assert {
+    ($condition:expr) => {
+        // Based on the latest one in `rustc`'s one before it was [removed].
+        //
+        // [removed]: https://github.com/rust-lang/rust/commit/c2dad1c6b9f9636198d7c561b47a2974f5103f6d
+        #[allow(dead_code)]
+        const _: () = [()][!($condition) as usize];
+    };
+}