Implicitly Captured Closure: a

implicitly-captured-closure.cs

internal static class Foobar
{
    private static Bar Foo(Func<Bar, Bar> f) => f(null);

    internal class Bar
    {
        public Bar Use(Bar bar) => throw new NotImplementedException();
    }

    internal static void Warning()
    {
        var a = new Bar();
        var b = new Bar();

        var foo = Foo(i => a.Use(b));
        var foo2 = Foo(i => b);
    }
}