public static ReadOnlyListExtensions.SelectAtEnumerable <ValueWrapper <TSource>, TSource, TResult, TSelector> SelectAt <TSource, TResult, TSelector>(
this ImmutableList <TSource> source,
TSelector selector = default)
where TSelector : struct, IFunction <TSource, int, TResult>
=> ReadOnlyListExtensions.SelectAt <ValueWrapper <TSource>, TSource, TResult, TSelector>(new ValueWrapper <TSource>(source), selector);