[GHC] #13755: GHC-8.0.2+ spits out $dm names in error messages

[GHC]

#13755: GHC-8.0.2+ spits out $dm names in error messages
-------------------------------------+-------------------------------------
        Reporter:  zilinc            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 I agree it's not great. But it's hard even to say what we'd ''like'' it to
 say, given that the error arises from filling in the default methods.
 What would you like it to say?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13755#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler