A 4GL variable used inside a subquery was never replaced by a placeholder and
never bound, so both the C and the C# back ends stopped with
Assertion failed: These should all have been removed by now... (sqlexpr.c)
and the statement could not be compiled at all.
make_list_item_list_from_select collects a statement's expressions so the back
ends can substitute variables for placeholders. Its E_SLI_IN_SELECT case walked
only complex_expr.left - the column being tested - and never the right, which is
the subquery. The E_SLI_SUBQUERY case below it does the right thing, but nothing
ever reached it, so nothing inside the subquery was collected.
The text writer already read both sides, so the collector was simply out of step
with it.
SELECT COUNT(*) INTO n FROM t WHERE k IN (SELECT a.k FROM u a WHERE a.c = v)
A constant in place of v compiled; a variable did not.
