Don't instantiate Module()s inside when() statements

[Øyvind Harboe]

So I did this and I got no compilation error, but of course it didn't work.

This made me curious: what does the below mean?

What are the inputs to this module outside of the when() clause? 

when (foo) {

   val bar = Module(Bar())

   bar.xxx := true.B

   ...

}

A bit more backround:

I have a def validate() function which expands to an assert(), where I wanted to place the assert and the code into a Validate() module to clean up RTL views. Hence I inadvertedly ended up with the module instantiation inside the when() statement.