[GHC] #13819: GHC Panics

[GHC]

#13819: GHC Panics
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           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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 {{{#!hs
 {-# LANGUAGE DeriveFunctor, TypeApplications #-}
 -- {-# Language ViewPatterns    #-}
 -- {-# Language InstanceSigs, ViewPatterns, TupleSections,
 GeneralizedNewtypeDeriving, TemplateHaskell, LambdaCase #-}

 module D where

 import Data.Coerce
 import Control.Applicative

 newtype A a = A (IO a)
   deriving Functor

 instance Applicative A where
   pure = pure @(_ -> WrappedMonad A _) @(_ -> A _) pure

 instance Monad A where
 }}}

 causes a panic

 {{{
 $ ghci -ignore-dot-ghci /tmp/a.hs
 GHCi, version 8.3.20170605: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling D                ( /tmp/a.hs, interpreted )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.3.20170605 for x86_64-unknown-linux):
         repSplitAppTys
   w0_a1xc[tau:4]
   WrappedMonad A w0_a1xe[tau:4]
   []
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in
 ghc:Outputable
         pprPanic, called at compiler/types/Type.hs:809:9 in ghc:Type

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

 >
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13819>
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