julia

12685822 - Make `bound_var_below` return `NULL` if the input typevar is not valid.

Make `bound_var_below` return `NULL` if the input typevar is not valid. If offset > 0, the correct result is `var - offset` if expressible. So an unbounded typevar should not be returned in this case as it might be a diagonal var. Since the result could be improved if `N` get fixed, set `intvalued` to 2 as a re-intersection hint.