[GHC] #16146: Trivial partial type signature kills type inference in the presence of GADTs

[GHC]

#16146: Trivial partial type signature kills type inference in the presence of
GADTs
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 I'm pleased to report that we have singletons
 [https://github.com/goldfirere/singletons/issues/357#issuecomment-452935291
 working again], but it will require users to write apparently-redundant
 type annotations in a few places. It would be nice to address this bug /
 design flaw so that singletons can become more ergonomic again.

 (Yes, I know this will have to go through the proposals process, but I
 still would like feedback here first.)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16146#comment:10>
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