I'm getting a message:
[babble_patch.ck]:line(142): arguments type(s) do not match:
[babble_patch.ck]:line(142): ... for function 'PatchableObserver.attach_all(...)' ...
[babble_patch.ck]:line(142): ...(please check the argument types)

The line in question in file babble_patch.ck:line(142):
PatchableObserver.attach_all(_handlers);
The declaration of _handlers in babble_patch.ck:line(76):
    Handler @ _handlers[];
The declaration of the Handler class in babble_patch.ck:line(37):
class Handler extends PatchableObserver { ... }

And the declaration of attach_all in patchable_observer.ck:line(16):
    fun static void attach_all(PatchableObserver ps[]) { ... }

What I *intend* is to pass an array of Handler objects to attach_all().  I can imagine that ChucK is concerned that Handler isn't the same as PatchableObject (don't laugh at me -- I've gotten used to Ruby's duck typing).  

But I can't figure out the syntax for casting an array of Handler[] as an array of PatchableObject[] to pass to attach_all().  Any ideas?

[If need be I can make a smaller self-contained example. But my hope is that this is some easily answered question.]

Thanks in advance,

- Rob