Crosscasting confusion, part 2

I'm still struggling with trying to match types against empty arrays. In this case, I have an array that was originally created like this:

var x: [X] = [] // X is a struct

This empty array is passed around as an 'Any' parameter:

func jValueForPValue (pValue: Any) -> AnyObject { …

and eventually I try to test if the parameter is an array:

     if let pArray = pValue as? [Any] { …

This test fails. If I set a breakpoint just after it fails, I get this:

(lldb) p pValue
error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0x80000007).
The process has been returned to the state before expression evaluation.
(lldb) frame v pValue
(Any) pValue = {
  payload_data_0 = 0x000000010247efa0 -> 0x000000010081cd70 _swiftEmptyArrayStorage
  payload_data_1 = 0x000000010247efa0 -> 0x000000010081cd70 _swiftEmptyArrayStorage
  payload_data_2 = 0x000000010247efa0 -> 0x000000010081cd70 _swiftEmptyArrayStorage
  instance_type = 0x000000010247efa0 -> 0x000000010081cd70 _swiftEmptyArrayStorage
}

I don't know what this means, or what to do about it.

The interesting thing is that the test for array succeeds at least sometimes, and in the case I looked at, the array was the empty one that was discussed in a previous thread, originally created inside a dictionary like this:

["key": [Any] ()]

Since an array passed as 'pValue' can in fact be an array of anything (Ints, Strings, structs, classes, collections), I don't know what test to use. Anyone got any ideas?