TH doesn't pretty-print classes without fundeps correctly

A class with no functional dependencies is pretty-printed with a spurious | character, like in this example:

class Abstraction c_0 a_1 |
    where abstractL :: forall m_2 . GHC.Base.Monad m_2 => c_0 ->
                                                          Control.Monad.State.StateT ([(Ident,
                                                                                        Term)])
                                                                                     m_2
                                                                                     a_1

Trac metadata

Trac field	Value
Version	6.6
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Multiple
Architecture	Multiple