STRING
@init{StringBuilder buf = new StringBuilder();}
    :
           '"'
           ( escaped=ESC {buf.append(escaped.getText());} |
             normal=~('"'|'\\'|'\n'|'\r')     {buf.appendCodePoint(normal);} )*
           '"'
           {setText(buf.toString());}
    ;

fragment
ESC
    :   '\\'
        (       '\n'    {setText("\\");}
        |       'r'    {setText("\r");}
        |       't'    {setText("\t");}
        |       'b'    {setText("\b");}
        |       'f'    {setText("\f");}
        )
    ;