In the case where someone writes an event similar to this one:
on *:TEXT:*:?:if (0) {
noop
}
mIRC reports that no close bracket was found, but does not specify the line number.
Furthermore, if the 0 is changed to a 1 then the code in the block will not be executed anyway. If this arrangement is not meant to be supported, perhaps a different error message could be added to cover both cases, complete with line number?
Edit:
Saturn pointed out that errors in one-line events don't give line numbers under any circumstances. For example, both:
and
on *:TEXT:*:?:{ echo -a }
simply report "/echo: insufficient parameters".