anchor.diff:      | constant
       | general_element
       | '(' subquery ')' subquery_operation_part*
  -    | '(' expressions_ ')'
  +    | '(' expressions ')'
       ;
   
   quantified_expression
  
positive.code:     ;
  
  open_statement
      : OPEN cursor_name ('(' expressions_? ')')?
      ;
  
  fetch_statement
  
negative.code:     : expression
      ;
  
  expressions
      : expression (',' expression)*
      ;
  
  