using System;

using System.Collections.Generic;

using System.Linq;

int[] xs = new[] { 1, 2, 3 };

IEnumerable<int> ys = xs.AsEnumerable();

Foo<IEnumerable<int>> foo1 = xs;

Foo<IEnumerable<int>> foo2 = ys;

Foo<IEnumerable<int>> foo3 = (Foo<IEnumerable<int>>)ys;

Console.WriteLine("Hello World");

​

public class Foo<T> {

    public T Bar;

    public Foo(T bar) => Bar = bar;

    public static implicit operator Foo<T>(T bar) => new(bar);

}