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