E lastWhere(bool test(E element), { E orElse() })

Returns the last element that satisfies the given predicate test.

An iterable that can access its elements directly may check its elements in any order (for example a list starts by checking the last element and then moves towards the start of the list). The default implementation iterates elements in iteration order, checks test(element) for each, and finally returns that last one that matched.

If no element satisfies test, the result of invoking the orElse function is returned. If orElse is omitted, it defaults to throwing a StateError.

Source 

E lastWhere(bool test(E element), {E orElse()}) {
  int length = this.length;
  for (int i = length - 1; i >= 0; i--) {
    E element = elementAt(i);
    if (test(element)) return element;
    if (length != this.length) {
      throw new ConcurrentModificationError(this);
    }
  }
  if (orElse != null) return orElse();
  throw IterableElementError.noElement();
}