#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 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler