Why doesn't this line throw a compile-time error?

[newpost]

List<Lazy<IA>> list = new List<System.Lazy<IA>>();

list.Add(new Lazy<IA>(()=>new A()));
list.Add(new Lazy<IA>(()=>new A()));
foreach(IA a in list) // Why doesn't this line throw a compile-time error?
{
	a.Run();
}
public interface IA
{
	void Run();
}

public class A:IA
{
	public void Run()
	{
		Console.WriteLine("A.Run");
	}
}

[ufcpp]

First, as a remnant from the days before Generics, foreach statement generates explicit casts.

https://github.com/dotnet/csharpstandard/blob/draft-v8/standard/statements.md#13952-synchronous-foreach

And converting a class to an interface results in an error only when the class is sealed.

https://github.com/dotnet/csharpstandard/blob/draft-v8/standard/conversions.md#1035-explicit-reference-conversions

var a = (IA)new A(); // A derived class may implement the interface.
var a1 = (IA)new A1();

var b = (IA)new B(); // Error only when the class is sealed

interface IA;
class A;
class A1 : A, IA;
sealed class B;

[newpost]

You're a genius!