Testing template parameter has given API

[NaN via Digitalmars-d-learn]

Howdy, any idea what Im doing wrong? Given a type T i want to 
test the presence of certain methods. I looked in phobos to see 
how isInputRange was defined but it didnt really help as all the 
methods have no parameters and it used some weird lamda stuff i 
think.

template isPathType(T)
{
    alias FloatType = ReturnType!(T.x);

    enum isPathType = (isFloatOrDouble!(FloatType)
        && (is(typeof(&T.x) == FloatType delegate(size_t idx)))
        && (is(typeof(&T.y) == FloatType delegate(size_t idx)))
        && (is(typeof(&T.cmd) == PathCmd delegate(size_t idx)))
        && (is(typeof(&T.points) == Point!FloatType 
delegate(size_t idx)))
        && (is(typeof(&T.length) == size_t delegate())));
}