gistfile1.txt

switch(FEAT_INDUSTRIES, PARENT, increment_town_monthly_cycle_industry_counter,
    [
        LOAD_PERM(${get_perm_num("this_cycle_industry_counter")}) < count_industries_in_town()
        ?
        STORE_PERM(
            LOAD_PERM(${get_perm_num("this_cycle_industry_counter")}) + 1,
            ${get_perm_num("this_cycle_industry_counter")}
        )
        :
        0
    ]) {
    return;
}

replace https://github.com/OpenTTD/nml/blob/master/nml/ast/switch.py#L130-L131 with

   def is_read_only(self):
        for result in [r.result for r in self.body.ranges] + [self.body.default]:
            if result is not None and result.value is not None:
                if not result.value.is_read_only():
                    return false
        return self.expr.is_read_only()