internal GroupEnumerator(LocalList <T> list, Func <T, TKey> keySelector, EqualityComparer <TKey> comparer)
{
var values = new LocalList <Row <TKey, T> >(list.Length);
var uniqueKeys = new LocalList <TKey>();
for (var i = 0; i < list.Length; i++)
{
var element = list.Get(i);
var key = keySelector(element);
values.Add(new Row <TKey, T>(key, element));
if (!uniqueKeys.Contains(key, comparer))
{
uniqueKeys.Add(key);
}
}
_comparer = comparer;
_current = default;
_position = 0;
_values = values;
_uniqueKeys = uniqueKeys;
}