[chuck-users] what is the syntax for casting an array of objects?

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