[GHC] #12784: Typechecker regression in GHC 8.0.2 involving DefaultSignatures

[GHC]

#12784: Typechecker regression in GHC 8.0.2 involving DefaultSignatures
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by rwbarton):

 I don't know exactly what changed in GHC here, but the current monad-
 logger code is utterly wrong and the "workaround" is actually just
 replacing the code with what the author doubtless meant to write in the
 first place.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12784#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler