[type]
Parser

[grammar]
grammar T;
s : a ;
a : {<False()>}? ID  {<writeln("\"alt 1\"")>}
  | {<True()>}?  INT {<writeln("\"alt 2\"")>}
  ;
ID : 'a'..'z'+ ;
INT : '0'..'9'+;
WS : (' '|'\n') -> skip ;

[start]
s

[input]
x

[errors]
"""line 1:0 no viable alternative at input 'x'
"""