Add type_on to simplify some code (#912)

No functional change.

Bench: 3344311

Author: protonspring

src/board.rs

@@ -184,6 +184,10 @@ impl Board {
         self.colored_pieces(color, PieceType::King).lsb()
     }
 
+    pub fn type_on(&self, square: Square) -> PieceType {
+        self.mailbox[square].piece_type()
+    }
+
     pub fn piece_on(&self, square: Square) -> Piece {
         self.mailbox[square]
     }

src/board/see.rs

@@ -89,7 +89,7 @@ impl super::Board {
     }
 
     fn move_value(&self, mv: Move) -> i32 {
-        let capture = self.piece_on(mv.capture_sq()).piece_type();
+        let capture = self.type_on(mv.capture_sq());
         let mut value = capture.value();
 
         if mv.is_promotion() {

src/movepick.rs

@@ -158,8 +158,8 @@ impl MovePicker {
 
         for entry in self.list.iter_mut() {
             let mv = entry.mv;
-            let captured = td.board.piece_on(mv.capture_sq()).piece_type();
-            let pt = td.board.piece_on(mv.from()).piece_type();
+            let captured = td.board.type_on(mv.capture_sq());
+            let pt = td.board.type_on(mv.from());
 
             entry.score = 16 * captured.value()
                 + td.noisy_history.get(threats, td.board.moved_piece(mv), mv.to(), captured)
@@ -213,7 +213,7 @@ impl MovePicker {
 
         for entry in self.list.iter_mut() {
             let mv = entry.mv;
-            let pt = td.board.piece_on(mv.from()).piece_type();
+            let pt = td.board.type_on(mv.from());
 
             entry.score = 2048 * td.quiet_history.get(threats, side, mv) / 1024
                 + 1536 * td.conthist(ply, 1, mv) / 1024

src/search.rs

@@ -725,7 +725,7 @@ fn search<NODE: NodeType>(
         let history = if is_quiet {
             td.quiet_history.get(td.board.all_threats(), stm, mv) + td.conthist(ply, 1, mv) + td.conthist(ply, 2, mv)
         } else {
-            let captured = td.board.piece_on(mv.to()).piece_type();
+            let captured = td.board.type_on(mv.to());
             td.noisy_history.get(td.board.all_threats(), td.board.moved_piece(mv), mv.to(), captured)
         };
 
@@ -1029,7 +1029,7 @@ fn search<NODE: NodeType>(
                 td.board.all_threats(),
                 td.board.moved_piece(best_move),
                 best_move.to(),
-                td.board.piece_on(best_move.to()).piece_type(),
+                td.board.type_on(best_move.to()),
                 noisy_bonus,
             );
         } else {
@@ -1043,7 +1043,7 @@ fn search<NODE: NodeType>(
         }
 
         for &mv in noisy_moves.iter() {
-            let captured = td.board.piece_on(mv.to()).piece_type();
+            let captured = td.board.type_on(mv.to());
             td.noisy_history.update(td.board.all_threats(), td.board.moved_piece(mv), mv.to(), captured, -noisy_malus);
         }
 
@@ -1292,7 +1292,7 @@ fn qsearch<NODE: NodeType>(td: &mut ThreadData, mut alpha: i32, beta: i32, ply:
                 td.board.all_threats(),
                 td.board.moved_piece(best_move),
                 best_move.to(),
-                td.board.piece_on(best_move.to()).piece_type(),
+                td.board.type_on(best_move.to()),
                 bonus,
             );
         } else {