Compounds don't support interpolation of variables

[isaacsas]

Which means they are not usable programmatically within code. For example

@variables t
@species A(t) B(t)
a = A
@compound AB a B   # errors
@compound AB $a B   # errors

So there is no way for a user to have a species stored in a variable and get it into the @compound macro.

[TorkelE]

That's annoying. Thought we had that in the tests, but apparently missed to point this out properly when I suggested them.

[isaacsas]

I thought so too, and definitely mentioned it, but somehow it was apparently missed.

[TorkelE]

now works on master