Can someone explain this error?

[Sean Kelly]

    class C
    {
        this() {}
        this( int x, int y ) {}
    }

    void main()
    {
        auto c = alloc!(C);
        auto d = alloc!(C)( 1, 2 );
    }

    T alloc(T, Params ...)( Params params )
    {
        return new T( params );
    }

$ dmd test
test.d(10): Error: expected 0 arguments, not 2