alloc_my_state
state = alloc_my_state(fn);
set_state_expr(my_id, expr, alloc_my_state(expr));
set_state_expr(my_id, left, alloc_my_state(get_switch_expr()));
set_state(my_id, name, sym, alloc_my_state(mod_expr, prev));
set_state(my_id, left_name, left_sym, alloc_my_state(right_name, right_sym));