anchor.diff:      ;
   
   constraint
  -    : brackettedExpression | builtInCall | functionCall
  +    : brackettedExpression
  +    | builtInCall
  +    | functionCall
       ;
   
   functionCall
  
positive.code: PATH;
  PATH_PRIMARY;
  PATH_NEGATED;
  }
  
  @header {
  
negative.code:     ;
  
  unaryExpression
      : op=NEGATION primaryExpression -> ^(UNARY_NOT[$op] /*NEGATION*/ primaryExpression)
      | op=PLUS primaryExpression -> ^(UNARY_PLUS[$op] /*PLUS*/ primaryExpression)
      | op=MINUS primaryExpression -> ^(UNARY_MINUS[$op] /*MINUS*/ primaryExpression)
      | primaryExpression -> ^(UNARY primaryExpression)
      ;
  
  primaryExpression
  