During install, network's Typeable.h clobbers base's copy
There are two copies of Typeable.h in a fully populated GHC tree. The copy in libraries/network/include is a cut-down version of the copy from libraries/base/include.
Unfortunately, the network copy overwrites the base copy when GHC is installed. Since the network version defines INSTANCE_TYPEABLE0 but not , anything that rquires one of the other definitions is going to break.
This affects hs-plugins, for example; I can't build it, because on my Fedora box, it's getting network's copy of Typeable.h.
It seems that a correct approach would be to drop the less-capable duplicate from the network tree.