Change pre-checking to be method-driven instead of event-driven, so we can get the return value.

lib/chess_bloc/chess_bloc.dart

@@ -8,7 +8,6 @@ class ChessBloc extends Bloc<ChessEvent, ChessBoardState> {
 
   ChessBloc._internal() : super(ChessBoardState.init()) {
     on<PieceMoved>(moveHandler);
-    on<PreCheckMove>(preCheckHandler);
   }
 
   factory ChessBloc.getInstance() {
@@ -36,11 +35,11 @@ class ChessBloc extends Bloc<ChessEvent, ChessBoardState> {
     ));
   }
 
-  void preCheckHandler(
+  bool preCheckHandler(
     PreCheckMove event,
-    Emitter<ChessBoardState> emit,
   ) {
     print('Pretending to check a move before you drop a piece');
+    return true;
   }
 }
 

lib/chessapp/chess_square.dart

@@ -54,8 +54,10 @@ class ChessSquare extends StatelessWidget {
         );
       },
       onWillAccept: (move) {
-        ChessBloc().add(PreCheckMove(move: move!));
-        return true;
+        final legalMove =
+            ChessBloc().preCheckHandler(PreCheckMove(move: move!));
+        print('onWillAccept returns $legalMove');
+        return legalMove;
       },
       onAccept: (move) {
         move.endSquare = coordinate;