[board] Add documentation to the types in castle.rs

board/src/castle.rs

@@ -17,10 +17,12 @@ pub struct Parameters {
     /// Target or destination squares for the king and rook.
     target: Squares,
 
-    /// The set of squares that must be clear of any pieces in order to perform this castle.
+    /// The set of squares that must be clear of any pieces in order to perform
+    /// this castle.
     clear: BitBoard,
 
-    /// The set of squares that must not be attacked in order to perform this castle.
+    /// The set of squares that must not be attacked (i.e. visible to opposing
+    /// pieces) in order to perform this castle.
     check: BitBoard,
 }
 
@@ -41,10 +43,14 @@ impl Parameters {
         self.target.rook
     }
 
+    /// A [`BitBoard`] of the squares that must be clear of any piece in order
+    /// to perform this castle move.
     pub fn clear_squares(&self) -> &BitBoard {
         &self.clear
     }
 
+    /// A [`BitBoard`] of the squares that must not be visible to opposing
+    /// pieces in order to perform this castle move.
     pub fn check_squares(&self) -> &BitBoard {
         &self.check
     }
@@ -60,7 +66,7 @@ impl Castle {
     pub const ALL: [Castle; 2] = [Castle::KingSide, Castle::QueenSide];
 
     /// Parameters for each castling move, organized by color and board-side.
-    const PARAMETERS: [[Parameters; 2]; 2] = [
+    const PARAMETERS: [[Parameters; 2]; Color::NUM] = [
         [
             Parameters {
                 origin: Squares {