src/librustc_data_structures/macros.rs

   1 /// A simple static assertion macro.
   2 #[macro_export]
   3 #[allow_internal_unstable(type_ascription)]
   4 macro_rules! static_assert {
   5     ($test:expr) => {
   6         // Use the bool to access an array such that if the bool is false, the access
   7         // is out-of-bounds.
   8         #[allow(dead_code)]
   9         const _: () = [()][!($test: bool) as usize];
  10     };
  11 }
  12
  13 /// Type size assertion. The first argument is a type and the second argument is its expected size.
  14 #[macro_export]
  15 macro_rules! static_assert_size {
  16     ($ty:ty, $size:expr) => {
  17         const _: [(); $size] = [(); ::std::mem::size_of::<$ty>()];
  18     };
  19 }