[GHC] #14628: Panic (No skolem Info) in GHCi

[GHC]

#14628: Panic (No skolem Info) in GHCi
-------------------------------------+-------------------------------------
           Reporter:  AndreasK       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  GHCi           |           Version:  8.2.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:  #13393
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Loading the following code in GHCi causes a panic.

 Versions affected at least 8.2.2 and 8.0.2

 {{{
 module Main where

 import System.IO
 import Control.Monad.IO.Class
 import Control.Monad.Trans.State
 import Text.Printf

 putArrayBytes :: Handle       -- ^ output file handle
               -> [String]     -- ^ byte-strings
               -> IO Int -- ^ total number of bytes written
 putArrayBytes outfile xs = do
   let writeCount x = modify' (+ length x) >> liftIO (putLine x) :: MonadIO
 m => StateT Int m ()
   execStateT (mapM_ writeCount xs) 0
   where putLine = hPutStrLn outfile . ("  "++) . concatMap (printf
 "0x%02X,")

 {-
 ghci:
 :break 12 46
 :trace putArrayBytes stdout [['1'..'9'],['2'..'8'],['3'..'7']]
 snd $ runStateT _result 0
 -}

 main = undefined
 }}}



 {{{
 Configuring GHCi with the following packages:
 GHCi, version 8.2.2: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( C:\test\test.hs, interpreted )
 Ok, one module loaded.
 Loaded GHCi configuration from C:\Users\Andi\AppData\Local\Temp\ghci34988
 \ghci-script
 *Main> :break 12 46
 Breakpoint 0 activated at C:\test\test.hs:12:46-63
 *Main> :trace putArrayBytes stdout [['1'..'9'],['2'..'8'],['3'..'7']]
 Stopped in Main.putArrayBytes.writeCount, C:\test\test.hs:12:46-63
 _result :: StateT Int m () = _
 putLine :: [Char] -> IO () = _
 x :: [Char] = "123456789"
 [C:\test\test.hs:12:46-63] [C:\test\test.hs:12:46-63] *Main> snd $
 runStateT _result 0

 <interactive>:3:7: error:<interactive>: panic! (the 'impossible' happened)
   (GHC version 8.2.2 for x86_64-unknown-mingw32):
         No skolem info:
   m_I5Cm[rt]
   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\typecheck\TcErrors.hs:2653:5 in
 ghc:TcErrors

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

 [C:\test\test.hs:12:46-63] [C:\test\test.hs:12:46-63] *Main> :r
 [1 of 1] Compiling Main             ( C:\test\test.hs, interpreted )
 Ok, one module loaded.
 *Main> :break 12 46
 Breakpoint 1 activated at C:\test\test.hs:12:46-63
 *Main> :trace putArrayBytes stdout [['1'..'9'],['2'..'8'],['3'..'7']]
 Stopped in Main.putArrayBytes.writeCount, C:\test\test.hs:12:46-63
 _result :: StateT Int m () = _
 putLine :: [Char] -> IO () = _
 x :: [Char] = "123456789"
 [C:\test\test.hs:12:46-63] [C:\test\test.hs:12:46-63] *Main> snd $
 runStateT _result 0

 <interactive>:7:7: error:<interactive>: panic! (the 'impossible' happened)
   (GHC version 8.2.2 for x86_64-unknown-mingw32):
         No skolem info:
   m_I5Nz[rt]
   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\typecheck\TcErrors.hs:2653:5 in
 ghc:TcErrors

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

 [C:\test\test.hs:12:46-63] [C:\test\test.hs:12:46-63] *Main>
 }}}

 Maybe related to #13393.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14628>
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