D opBinary error

import std.stdio;


class Foo(uint something)
{
	Foo opBinary(string op)(Foo rhs) const
    if (op == "*")
	{
		writeln("calling Foo.*");
	}
}

class Bar : Foo!(3)
{}

class Baz : Foo!(4)
{}

void main()
{
	auto bar = new Bar();
	auto baz = new Baz();

	auto foo = bar * baz; 
	// errors with 
	// tinker.d(25): Error: 'cast(Object)bar' is not of arithmetic type, it is a object.Object
  // tinker.d(25): Error: 'baz' is not of arithmetic type, it is a tinker.Baz
}