[bitboard,core,position] Address a bunch of clippy warnings

position/src/position/piece_sets.rs

@@ -78,7 +78,7 @@ impl PieceBitBoards {
     }
 
     pub(super) fn place_piece(&mut self, piece: &PlacedPiece) -> Result<(), PlacePieceError> {
-        self.place_piece_with_strategy(piece, Default::default())
+        self.place_piece_with_strategy(piece, PlacePieceStrategy::default())
     }
 
     pub(super) fn place_piece_with_strategy(

position/src/position/position.rs

@@ -138,22 +138,27 @@ impl Position {
         })
     }
 
-    /// Return a BitBoard representing the set of squares containing a piece.
+    /// A [BitBoard] representing the set of squares containing a piece.
     #[inline]
+    #[must_use]
     pub(crate) fn occupied_squares(&self) -> &BitBoard {
         &self.pieces.all_pieces()
     }
 
     #[inline]
+    #[must_use]
     pub(crate) fn friendly_pieces(&self) -> &BitBoard {
         self.pieces.all_pieces_of_color(self.color_to_move)
     }
 
     #[inline]
+    #[must_use]
     pub(crate) fn opposing_pieces(&self) -> &BitBoard {
         self.pieces.all_pieces_of_color(self.color_to_move.other())
     }
 
+    #[inline]
+    #[must_use]
     pub(crate) fn all_pieces(&self) -> (&BitBoard, &BitBoard) {
         (self.friendly_pieces(), self.opposing_pieces())
     }
@@ -161,6 +166,7 @@ impl Position {
     /// Return a BitBoard representing the set of squares containing a piece.
     /// This set is the inverse of `occupied_squares`.
     #[inline]
+    #[must_use]
     pub(crate) fn empty_squares(&self) -> BitBoard {
         !self.occupied_squares()
     }