this_actually_works.cs

void Main() {
	var s = new S();
	foreach (var x in s) {}
}

struct S {
	public SpanSplitEnumerator GetEnumerator() => new SpanSplitEnumerator();
}

ref struct SpanSplitEnumerator {
	public Span<char> Current => throw new NotImplementedException();

	public void Dispose() {	}

	public bool MoveNext() {
		throw new NotImplementedException();
	}

	public void Reset() {
		throw new NotImplementedException();
	}
}