[GHC] #13998: Default Signature messes up arity of type constructor

[GHC]

#13998: Default Signature messes up arity of type constructor
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        Reporter:  andrewthad        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      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 RyanGlScott):

 Just as well, perhaps the `k` in `$dmeqForallPoly` shouldn't be available
 for visible type application in the first place. Indeed, the code which
 generates `Main.$dmeqForallPoly @(Main.Value)` already
 [http://git.haskell.org/ghc.git/blob/d7b17517e26007f537feab490509c0e13e0e239a:/compiler/typecheck/TcInstDcls.hs#l1569
 filters out] invisible type arguments, but it seems that the `k` in
 `$dmeqForallPoly` isn't properly marked as invisible.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13998#comment:3>
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