Add 'static_assert' macro

src/lib.rs

@@ -1 +1,2 @@
 pub mod board;
+pub mod utils;

src/utils/mod.rs

@@ -0,0 +1,2 @@
+pub mod static_assert;
+pub use static_assert::*;

src/utils/static_assert.rs

@@ -0,0 +1,28 @@
+//! Static assert.
+
+/// Assert a condition at compile-time.
+///
+/// See [RFC 2790] for potential addition into Rust itself.
+///
+/// [RFC 2790]: https://github.com/rust-lang/rfcs/issues/2790
+///
+/// # Examples
+///
+/// ```
+/// use seer::utils::static_assert;
+///
+/// static_assert!(42 > 0);
+/// ```
+#[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];
+    };
+}
+
+// I want it namespaced, even though it is exported to the root of the crate by `#[macro_export]`.
+pub use static_assert;