using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

​

//https://github.com/dotnet/runtime/issues/27552

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        //  Console.WriteLine($"There are {GetBugs().Count} bugs in casting Enumerable.Empty<T> to IList<T>");

        //Unhandled exception. System.InvalidCastException: Unable to cast object of type 'System.Linq.EmptyPartition`1[System.Int32]' to type 'System.Collections.Generic.IList`1[System.Int32]'.

        //at Program.GetBugs()

        Console.WriteLine($"{GetBugs2()}");

    }

​

    private static IList<int> GetBugs()

    {

        return (IList<int>)Enumerable.Empty<int>();

    }

​

    private static bool GetBugs2()

    {

        IEnumerable<int> v = Enumerable.Empty<int>();

        //v = new[]{1};     

        switch (v)

        {

            case ICollection { Count: > 0 } l:

                Console.WriteLine("ICollection { Count: > 0 }");

                return true;

            case IList l:

                Console.WriteLine("IList");

                return false;

            case ICollection l:

                Console.WriteLine("ICollection");

                return false;

            case IEnumerable l3:

                Console.WriteLine($"IEnumerable {v.Count()}  {l3.GetType()}");

                return false;

            default:

                Console.WriteLine("Undefined");

                return false;

        }

    }

}