anchor.diff:      node.accept(this);
     }
   
  -  void visitCommaSeparated(List<Node> nodes, int hasRequiredType,
  -      {bool newInForInit, bool newAtStatementBegin}) {
  +  void visitCommaSeparated(List<Expression> nodes, int hasRequiredType,
  +      {required bool newInForInit, required bool newAtStatementBegin}) {
       for (int i = 0; i < nodes.length; i++) {
         if (i != 0) {
           atStatementBegin = false;
  
positive.code:     }
      visitNestedExpression(assignment.leftHandSide, CALL,
          newInForInit: inForInit, newAtStatementBegin: atStatementBegin);
      if (assignment.value != null) {
        if (op != null) out(op);
        out('='); // '='
        visitNestedExpression(assignment.value, ASSIGNMENT,
            newInForInit: inForInit, newAtStatementBegin: false);
      }
    }
  
    @override
  
negative.code:         rightHandSide is LiteralNumber &&
          rightHandSide.value == "1") {
        // Output 'a += 1' as '++a' and 'a -= 1' as '--a'.
        _outputIncDec(op!, assignment.leftHandSide);
        return;
      }
      if (!assignment.isCompound &&
          leftHandSide is VariableUse &&
          rightHandSide is Binary) {
        final rLeft = rightHandSide.left;
        final rRight = rightHandSide.right;
        String op = rightHandSide.op;
        if (op == '+' ||
            op == '-' ||
  