anchor.diff:  
     bool visitParenthesizedExpression(ast.ParenthesizedExpression node) {
       return maybeAdd(node, visit(node.expression));
  +  }
  +
  +  bool visitPostfixExpression(ast.PostfixExpression node) {
  +    return maybeAdd(node, visit(node.operand));
     }
   
     bool visitPrefixedIdentifier(ast.PrefixedIdentifier node) {
  
positive.code:           _asCascadeSection(node.leftHandSide), node.operator.type,
            node.rightHandSide);
      }
    }
  
    visitCascadeExpression(ast.CascadeExpression node) => (f, s) {
  
negative.code:     return visit(node.expression)(f, s);
    };
  
    visitPostfixExpression(ast.PostfixExpression node) => (f, s) {
      return visit(node.operand)(f, (expr) {
        return s(AstFactory.postfixExpression(expr, node.operator.type));
      });
    };
  
    visitPrefixExpression(ast.PrefixExpression node) => (f, s) {
      return visit(node.operand)(f, (expr) {
  