Stashbox by Peter Csajtai

<PackageReference Include="Stashbox" Version="3.1.0-preview-544" />

.NET API 153,600 bytes

ImmutableArray<TValue>

sealed class ImmutableArray<TValue> : IEnumerable<TValue>, IEnumerable

public static readonly ImmutableArray<TValue> Empty

public int Length

public TValue this[int i] { get; }

public ImmutableArray()

public ImmutableArray<TValue> Add(TValue value)

public IEnumerator<TValue> GetEnumerator()