node requested directionality on 'FlitTypes' must be hardware, not a bare Chisel type. Perhaps you forgot to wrap it in Wire(_) or IO(_)?

Bug Report:

I want to test Queue API，and I define the element of queue called "Flit".
When I poke value to flit_type(which is a ChiselEnum type)，chisel report error.
So how can I poke value to ChiselEnum type?or choose another plan to achieve that?

My Environment:

Reproduce the Queue API example from the report and inspect how the Flit element declares FlitTypes and how the test pokes flit_type. Read the ChiselEnum, Wire(_), and IO(_) behavior implicated by the error. Done means the example has a verified way to drive the ChiselEnum without the requested-directionality error.

Written by the indexing model from the issue text.