[notes]
Loopback doesn't eval predicate at start of alt

[type]
Parser

[grammar]
grammar T;
file_
@after {<ToStringTree("$ctx"):writeln()>}
  : para para EOF ;
para: paraContent NL NL ;
paraContent : ('s'|'x'|{<LANotEquals("2",{T<ParserToken("Parser", "NL")>})>}? NL)+ ;
NL : '\n' ;
s : 's' ;
X : 'x' ;

[start]
file_

[input]
"""s


x

"""

[output]
"""(file_ (para (paraContent s) \n \n) (para (paraContent \n x) \n \n) <EOF>)
"""