Replace debug asserts with static_assertions

To check that transmutes will work correctly without having to rely on
error-prone runtime checking, the `static_assertions` crate has been
introduced. This allows comparing the size of types at compile time,
preventing potentially silent breakage.

This fixes #1417.

2 files changed, 2 insertions, 1 deletions

diff --git a/src/input.rs b/src/input.rs
index aa00ee3d..701feea1 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -137,7 +137,7 @@ impl<T> Binding<T> {
     /// Optimized to use single check instead of four (one per modifier)
     #[inline]
     fn mods_match(&self, mods: ModifiersState) -> bool {
-        debug_assert!(4 == mem::size_of::<ModifiersState>());
+        assert_eq_size!(ModifiersState, u32);
         unsafe {
             mem::transmute_copy::<_, u32>(&self.mods) == mem::transmute_copy::<_, u32>(&mods)
         }
diff --git a/src/lib.rs b/src/lib.rs
index d6229ee7..d9006fe0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -21,6 +21,7 @@
 #[macro_use] extern crate clap;
 #[macro_use] extern crate log;
 #[macro_use] extern crate serde_derive;
+#[macro_use] extern crate static_assertions;
 
 #[cfg(any(target_os = "linux", target_os = "freebsd", target_os="dragonfly", target_os="openbsd"))]
 extern crate x11_dl;