[GHC] #11311: segmentation fault/panic with -XTypeInType and functions of type * -> *

[GHC]

#11311: segmentation fault/panic with -XTypeInType and functions of type * -> *
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           Reporter:  rwbarton       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.11
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Since `* :: *`, I can specialize a function of type `a -> a` to type `* ->
 *`. This seems like potentially not a great idea, and GHCi agrees:
 {{{
 rwbarton at morphism:/tmp$ ~/ghc-newest/inplace/bin/ghc-stage2 --interactive
 GHCi, version 7.11.20151228: http://www.haskell.org/ghc/  :? for help
 Prelude> :set -XTypeInType
 Prelude> import Data.Kind
 Prelude Data.Kind> :t id :: * -> *
 id :: * -> * :: * -> *
 Prelude Data.Kind> (id :: * -> *) undefined `seq` ()
 Segmentation fault
 }}}

 Also, when compiling a module containing the above expression, I get a
 panic while producing Cmm:
 {{{
 rwbarton at morphism:/tmp$ ~/ghc-newest/inplace/bin/ghc-stage2 t
 [1 of 1] Compiling Main             ( t.hs, t.o )
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 7.11.20151228 for x86_64-unknown-linux):
         idToReg sat_sKV
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11311>
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