This has a couple of examples illustrating a problem I ran into. Some datatypes and functions are defined in Lib.hs, but trying to convert them into PLC in Main.hs causes a plugin error when you try to run the program:
tx-problem-exe: Error: Unsupported feature: Kind: * -> TYPE ('GHC.Types.TupleRep '[ 'GHC.Types.LiftedRep])
Context: Compiling kind: *
-> TYPE ('GHC.Types.TupleRep '[ 'GHC.Types.LiftedRep])
stack run should reproduce this, although stack.yaml will have to
be modified to point to the correct Plutus directory.
I'm not sure whether this is a genuine problem or if I just shouldn't be trying to do it.