check_cycle_lhs_try
static void check_cycle_lhs_try(struct node *stmtnp, struct node *lhs,
check_cycle_lhs_try(stmtnp, trylhs, tryrhs);
check_cycle_lhs_try(stmtnp, lhs->u.expr.left, rhs);
check_cycle_lhs_try(stmtnp, lhs->u.expr.right, rhs);