[GHC] #8461: Panic (on woefully incorrect code)

19 Oct 2013

      #8461: Panic (on woefully incorrect code)
-----------------------------------+---------------------------------------
       Reporter:  srhb             |             Owner:
           Type:  bug              |            Status:  new
       Priority:  low              |         Milestone:
      Component:  Compiler         |           Version:  7.6.3
       Keywords:                   |  Operating System:  Unknown/Multiple
   Architecture:                   |   Type of failure:  Compile-time crash
  Unknown/Multiple                 |         Test Case:
     Difficulty:  Unknown          |          Blocking:
     Blocked By:                   |
Related Tickets:                   |
-----------------------------------+---------------------------------------
 The following (very wrong) code causes a panic. The haskeline hackage
 package is required.

 {{{
 import System.Console.Haskeline
 import Control.Monad.State.Strict

 main = runStateT (runInputT settings loop) 0
    where
        loop = do
          minput <- lift getInputLine "% "
          loop

 settings :: Settings (StateT Int IO)
 settings = setComplete comp defaultSettings
 comp _ = do
   n <- get
   put (n+1)
   return ("", [Completion (show n) "" True])

 }}}

 The error:

 {{{
 [1 of 1] Compiling Main             ( test.hs, test.o )

 test.hs:7:20:
     Couldn't match kind `* -> *' with `*'
     Expected type: [Char] -> InputT m0 (Maybe String)
       Actual type: [Char] -> InputT m0 (Maybe String)
     Kind incompatibility when matching types:
       [Char] :: * -> *
       [Char] :: *
     The function `lift'ghc: panic! (the 'impossible' happened)
   (GHC version 7.6.3 for x86_64-unknown-linux):
         kindFunResult ghc-prim:GHC.Prim.*{(w) tc 34d}

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

 PS: It was not clear to me whether to call this a compile-time crash or
 not. All I know is that the 'impossible' happened. :)

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8461
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