namespace System.Collections.Frozen
{
    public static class FrozenDictionary
    {
        public static FrozenDictionary<TKey, TValue>! ToFrozenDictionary<TKey, TValue>(this IEnumerable<KeyValuePair<TKey, TValue>>! source, IEqualityComparer<TKey>? comparer = null)
            where TKey, notnull;
    }
}