hash.c:855
static int
equal_i(key, val1, data)
    VALUE key, val1;
    struct equal_data *data;
{
    VALUE val2;

    if (key == Qundef) return ST_CONTINUE;
    if (!st_lookup(data->tbl, key, &val2)) {
	data->result = Qfalse;
	return ST_STOP;
    }
    if (!rb_equal(val1, val2)) {
	data->result = Qfalse;
	return ST_STOP;
    }
    return ST_CONTINUE;
}
