Let this() figure out T implicitly?

[kraybourne]

Hi!

This doesn't work:
        import std.stdio;
        class Foo(T)
        {
                T t;
                this(T val)
                {
                        t = val;
                }
        }

        void main()
        {
                auto o = new Foo(5);
        }
        _____

        $ dmd foo
        foo.d(13): Error: class foo.Foo(T) is used as a type
        $ _

So I must

        auto o = new Foo!(int)(5);

Then it compiles. Is it possible to have this() figure out the type some 
way? (In this particular example it's perhaps not such a big deal. But 
imagine a lot more args.)

(Side note: What _does_ that error message mean? I don't get it.)

thanks
/krbrn