[notes]
In this case, we're passing a parameter into a rule that uses that
information to predict the alternatives. This is the special case
where we know exactly which context we are in. The context stack
is empty and we have not dipped into the outer context to make a decision.

[type]
Parser

[grammar]
grammar T;
@parser::members {<InitIntMember("i","0")>}
s : a[2] a[1];
a[int i]
  : {<ValEquals("$i","1")>}? ID {<writeln("\"alt 1\"")>}
  | {<ValEquals("$i","2")>}? ID {<writeln("\"alt 2\"")>}
  ;
ID : 'a'..'z'+ ;
INT : '0'..'9'+;
WS : (' '|'\n') -> skip ;

[start]
s

[input]
a b

[output]
alt 2
alt 1