## Prelude I just decided to try haskell so please excuse possible lack of knowledge. Also i feel like this is rather an lsp error, however the error says "Please report this as a GHC bug" so I'll obey. ## Summary Typing in a simple haskell programm will crash the lsp with following message: ``` haskell-language-server-9.10.3.exe: internal error: ARR_WORDS object (00007ff45509d638) entered! (GHC version 9.10.3 for x86_64_unknown_mingw32) Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug haskell-language-server-wrapper.exe: Uncaught exception ghc-internal:GHC.Internal.IO.Exception.IOException: ``` ## Steps to reproduce On a x86_64 Windows machine. Downloaded the latest GHC from `https://www.haskell.org/ghc/download_ghc_9_10_3.html#windows64` and added the ../bin folder to my path. Downloaded the haskell-Language-server from `https://downloads.haskell.org/~hls/haskell-language-server-2.12.0.0/`. Created a Main.hs with following content: ``` main :: IO () main = do content <- readFile "input.csv" let ls = lines content let colNames = head' ls print colNames print $ unlines ls head' (x:_) = x ``` Started ghci and set the editor to nvim. Loaded Main.hs Note: I just started typing the **let**. ``` main :: IO () main = do content <- readFile "input.csv" let ls = lines content let colNames = head' ls le -- started typing here print colNames print $ unlines ls head' (x:_) = x ``` This will crash the lsp with the ## Full Trace ``` ❯ cat .\Main.hs main :: IO () main = do content <- readFile "input.csv" let ls = lines content let colNames = head' ls le -- writeFile "./output.txt" $ unlines ls head' (x:_) = x ❯ haskell-language-server-wrapper No 'hie.yaml' found. Try to discover the project type! Run entered for haskell-language-server-wrapper(haskell-language-server-wrapper.exe) Version 2.12.0.0, Git revision 7d983de4fa7ff54369f6dd31444bdb9869aec83e (dirty) x86_64 ghc-9.12.2 Current directory: C:\Users\zian\haskell Operating system: mingw32 Arguments: [] Cradle directory: C:\Users\zian\haskell Cradle type: Default Tool versions found on the $PATH cabal: Not found stack: Not found ghc: 9.10.3 Consulting the cradle to get project GHC version... 2025-11-07T13:33:42.174696Z | Debug | ghc --numeric-version Project GHC version: 9.10.3 haskell-language-server exe candidates: ["haskell-language-server-9.10.3.exe","haskell-language-server.exe"] Launching haskell-language-server exe at:C:\Users\zian\haskell-language-server-2.12.0.0-x86_64-mingw64\haskell-language-server-9.10.3.exe 2025-11-07T13:33:42.197373Z | Info | haskell-language-server version: 2.12.0.0 (GHC: 9.10.3) (PATH: C:\Users\zian\haskell-language-server-2.12.0.0-x86_64-mingw64\haskell-language-server-9.10.3.exe) (GIT hash: 7d983de4fa7ff54369f6dd31444bdb9869aec83e) 2025-11-07T13:33:42.204520Z | Info | Directory: C:\Users\zian\haskell 2025-11-07T13:33:42.206533Z | Info | Logging heap statistics every 60.00s ghcide setup tester in C:\Users\zian\haskell. Report bugs at https://github.com/haskell/haskell-language-server/issues Step 1/4: Finding files to test in C:\Users\zian\haskell Found 1 files Step 2/4: Looking for hie.yaml files that control setup Found 1 cradle () Step 3/4: Initializing the IDE Step 4/4: Type checking the files 2025-11-07T13:33:42.229403Z | Info | Cradle path: Main.hs 2025-11-07T13:33:42.229403Z | Warning | No [cradle](https://github.com/mpickering/hie-bios#hie-bios) found for Main.hs. Proceeding with [implicit cradle](https://hackage.haskell.org/package/implicit-hie). You should ignore this message, unless you see a 'Multi Cradle: No prefixes matched' error. 2025-11-07T13:33:42.235402Z | Info | invoking build tool to determine build flags (this may take some time depending on the cache) 2025-11-07T13:33:42.338814Z | Info | Interface files cache directory: C:\Users\zian\AppData\Local\ghcide\main-da39a3ee5e6b4b0d3255bfef95601890afd80709-da39a3ee5e6b4b0d3255bfef95601890afd80709 2025-11-07T13:33:42.343827Z | Info | Making new HscEnv. In-place unit ids: [ main-da39a3ee5e6b4b0d3255bfef95601890afd80709 ] 2025-11-07T13:33:42.538025Z | Info | Add dependency C:\Users\zian\haskell\Main.hs [] haskell-language-server-9.10.3.exe: internal error: ARR_WORDS object (00007ff4958a9fd8) entered! (GHC version 9.10.3 for x86_64_unknown_mingw32) Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug haskell-language-server-wrapper.exe: Uncaught exception ghc-internal:GHC.Internal.IO.Exception.IOException: callProcess: C:\Users\zian\haskell-language-server-2.12.0.0-x86_64-mingw64\haskell-language-server-9.10.3.exe (exit -1073740791): failed HasCallStack backtrace: ioError, called at libraries\process\System\Process.hs:379:7 in process-1.6.25.0-4f52:System.Process ```