const nits

src/bitboard.rs

@@ -63,6 +63,8 @@ impl BitBoard {
         self.0 &= !(1 << index)
     }
 
+    // PERF! was going to optimize setting multiple indexes,
+    // seems rust does this for us: https://godbolt.org/z/ddj3dMxsP
     #[cfg(not(feature = "bitvec"))]
     const fn set_bit(&mut self, index: usize) {
         self.0 |= 1 << index
@@ -84,7 +86,7 @@ impl BitBoard {
 
     // works on both `bitvec` and native (const on native)
     #[const_fn(cfg(not(feature = "bitvec")))]
-    pub fn count(&self) -> usize {
+    pub const fn count(&self) -> usize {
         self.0.count_ones() as usize
     }
 }