Don't report unclosed comments as "no newline at end of file". If we get EOF in the "middle" of a line but there's a newline at the end of the buffer we've got, it's because we're in the middle of a comment. So, say so.

1.
;
2.
(a, );
(, b);
( , );
(a,);
(,b);
(,);
3.
(a, b, );
(a, , c);
(, , c);
(a, , );
(, b, );
(, , c);
(, , )
(a,b,);
(a,,c);
(,,c);
(a,,);
(,b,);
(,,c);
(,,)