[notes]
This is a regression test for #270 "Fix operator += applied to a set of
tokens".  https://github.com/antlr/antlr4/issues/270

[type]
Parser

[grammar]
grammar T;
a : b b* ';' ;
b : ID val+=(INT | FLOAT)*;
ID : 'a'..'z'+ ;
INT : '0'..'9'+;
FLOAT : [0-9]+ '.' [0-9]+;
WS : (' '|'\n') -> skip ;

[start]
a

[input]
abc 34;

