[notes]
Test for https://github.com/antlr/antlr4/issues/958

[type]
Lexer

[grammar]
lexer grammar L;
T : 'a' {<True()>}? ;

[input]
aaa

[output]
[@0,0:0='a',<1>,1:0]
[@1,1:1='a',<1>,1:1]
[@2,2:2='a',<1>,1:2]
[@3,3:2='<EOF>',<-1>,1:3]