** (Response Object) - 
** Use to explicitly invoke Fantom methods. 
**   syntax: fantom
**   MethodCall(MyHandler#process, ["arg1", "arg2"]).toImmutableFunc
** Note that:
**  - if the method belongs to an 'IoC' service, the class instance is obtained from afIoc. 
**  - if the method belongs to a 'const' class, a new instance is created and cached. 
**  - non-const classes are cached for the duration of the request only.    
**  - methods are called using 'afIoc::Registry.callMethod(...)' so may have services as parameters. 
class MethodCall {
    ** The method to be called 
    const Method    method
    ** The arguments the method is to be called with 
          Obj?[]    args
    ** Creates a 'MethodCall'.
    new make(Method method, Obj?[] args := Obj#.emptyList) {
        this.method = method
        this.args   = args
    ** Returns an immutable func that represents this method call. 
    ** May be used as a response object itself.
    ** If this 'MethodCall' wraps an instance method (not static) then the func's first (and only) 
    ** argument must be the target object. Otherwise the func takes no arguments.
    ** TODO: Suggest design ideas for [implementing Obj.toImmutable()]``
    virtual Func toImmutableFunc() {
        iMeth := this.method
        iArgs := this.args.toImmutable
        if (iMeth.isStatic)
            return |->Obj?| {
        func := |Obj target -> Obj?| {
            iMeth.callOn(target, iArgs)
        }.toImmutable   // needed else the retype isn't immutatble
        // this is some hardcore reflective shit going down here!
        targetType := iMeth.parent
        funcType := Func#.parameterize(["A":targetType, "R":Obj?#])
        return func.retype(funcType).toImmutable
    override Str toStr() {