equals method

@override bool equals(Iterable<E>? elements1, Iterable<E>? elements2)

Compare two elements for being equal.

This should be a proper equality relation.

Implementation

@override
bool equals(T? elements1, T? elements2) {
  if (identical(elements1, elements2)) {
    return true;
  }
  if (elements1 == null || elements2 == null) {
    return false;
  }
  final HashMap<E, int> counts = HashMap<E, int>(
    equals: _elementEquality.equals,
    hashCode: _elementEquality.hash,
    isValidKey: _elementEquality.isValidKey,
  );
  int length = 0;
  for (final E e in elements1) {
    final int count = counts[e] ?? 0;
    counts[e] = count + 1;
    length++;
  }
  for (final E e in elements2) {
    final int? count = counts[e];
    if (count == null || count == 0) {
      return false;
    }
    counts[e] = count - 1;
    length--;
  }
  return length == 0;
}