[GHC] #13738: TypeApplications-related GHC internal error

[GHC]

#13738: TypeApplications-related GHC internal error
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  simonpj
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:  fixed             |             Keywords:
                                     |  TypeApplications
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Compile-time      |            Test Case:
  crash or panic                     |  polykinds/T13738
      Blocked By:                    |             Blocking:
 Related Tickets:  #13985            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 FWIW, I didn't notice #14209 in a package in the wild, only when stress-
 testing different ways of implicitly binding kind variables. And indeed,
 it doesn have a workaround. Instead of writing this:

 {{{#!hs
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE TypeInType #-}
 module Bug where

 data MyProxy k (a :: k) = MyProxy
 data Foo (z :: MyProxy k (a :: k))
 }}}

 You can write this:

 {{{#!hs
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE TypeInType #-}
 module Bug where

 data MyProxy k (a :: k) = MyProxy
 data Foo (z :: MyProxy k a)
 }}}

 So I would be OK with not merging that patch.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13738#comment:21>
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