DotNext by Roman Sakno

<PackageReference Include="DotNext" Version="1.2.0" />

.NET API 245,248 bytes

SingletonList<T>

struct SingletonList<T> : IReadOnlyList<T>, IEnumerable<T>, IEnumerable, IReadOnlyCollection<T>

public Enumerator<T> GetEnumerator()

Gets enumerator for the single element in the list.