anchor.diff:      ;
   
   select 
  -    : withClause_? unionSelect
  +    : withClause_? unionClause_
       ;
   
   withClause_
  
positive.code:     ;
  
  subquery
      : LP_ unionSelect RP_
      ;
  
negative.code:     : ignoredIdentifier_ columnNames? AS subquery
      ;
  
  unionClause_
      : selectExpression (UNION (ALL | DISTINCT)? selectExpression)*
      ;
  
  