"lookupGREInfo: lookup failed" error involving TemplateHaskell and re-exports

[adamgundry]

Your environment

Which OS do you use? Linux Mint
Which version of GHC do you use and how did you install it? 9.14.1 from ghcup
How is your project built? https://github.com/adamgundry/hls-bug

Which LSP client (editor/plugin) do you use? VSCode+vscode-haskell
Which version of HLS do you use and how did you install it? 2.14.0.0 from ghcup
Have you configured HLS in any way? No

haskell-language-server version: 2.14.0.0 (GHC: 9.10.3) (PATH: /home/adam/.ghcup/hls/2.14.0.0/lib/haskell-language-server-2.14.0.0/bin/haskell-language-server-wrapper)
Tool versions found on the $PATH
cabal:          3.16.1.0
stack:          3.3.1
ghc:            9.14.1

Steps to reproduce

Check out the example at https://github.com/adamgundry/hls-bug (minimized from a big private project). This is a multi-component project with two components comp-a and comp-b, where both use TemplateHaskell. The module A contains a definition of foo (generated from a TH splice), which module A2 re-exports. Module B then imports it via A2, and references it via another TH splice.

Opening B.hs, A2.hs and A.hs in VSCode then making changes (e.g. changing import A2 to import A and back, or modifying the exports of A2) occasionally results in the following error at the top of B.hs:

lookupGREInfo

lookup failed: foo
Call stack:
    CallStack (from HasCallStack):
      pprPanic, called at compiler/GHC/Rename/Env.hs:2030:15 in ghc-9.14.1-3f81:GHC.Rename.Env
Please report this bug to the compiler authors.

I have occasionally seen other issues, such as failures to load interface files, or an incorrect claim that A2 does not export foo. The issues seem to be somewhat nondeterministic, and only seem to happen when making edits to the project. In particular, running haskell-language-server-wrapper-2.14.0.0 typecheck succeeds (see log below).

This seems somewhat similar to https://gitlab.haskell.org/ghc/ghc/-/work_items/27227 / haskell/cabal#7684.

Debug information

$ haskell-language-server-wrapper-2.14.0.0 typecheck
No 'hie.yaml' found. Try to discover the project type!
Run entered for haskell-language-server-wrapper(haskell-language-server-wrapper-2.14.0.0) Version 2.14.0.0 x86_64 ghc-9.10.3
Current directory: /home/adam/Documents/Well-Typed/Code/hls-bug
Operating system: linux
Arguments: ["typecheck","--cwd","/home/adam/Documents/Well-Typed/Code/hls-bug"]
Cradle directory: /home/adam/Documents/Well-Typed/Code/hls-bug
Cradle type: Cabal

Tool versions found on the $PATH
cabal:          3.16.1.0
stack:          3.3.1
ghc:            9.14.1


Consulting the cradle to get project GHC version...
2026-08-26T13:14:05.352202Z | Debug | cabal --numeric-version
2026-08-26T13:14:05.381468Z | Debug | cabal --builddir=/home/adam/.cache/hie-bios/dist-hls-bug-9e0fe59a9b659bf2c06b27ac4ecca845 path --output-format=json
2026-08-26T13:14:05.409047Z | Debug | /home/adam/.ghcup/bin/ghc --numeric-version
Project GHC version: 9.14.1
haskell-language-server exe candidates: ["haskell-language-server-9.14.1","haskell-language-server"]
Launching haskell-language-server exe at:/home/adam/.ghcup/bin/haskell-language-server-9.14.1
2026-08-26T13:14:05.440917Z | Debug | cabal --builddir=/home/adam/.cache/hie-bios/dist-hls-bug-9e0fe59a9b659bf2c06b27ac4ecca845 path --output-format=json
2026-08-26T13:14:05.543492Z | Debug | /home/adam/.ghcup/bin/ghc -v0 -package-env=- -ignore-dot-ghci -e Control.Monad.join (Control.Monad.fmap System.IO.putStr System.Environment.getExecutablePath)
2026-08-26T13:14:05.573663Z | Debug | cabal --builddir=/home/adam/.cache/hie-bios/dist-hls-bug-9e0fe59a9b659bf2c06b27ac4ecca845 path --output-format=json
2026-08-26T13:14:05.603037Z | Debug | /home/adam/.ghcup/bin/ghc --print-libdir
2026-08-26T13:14:06.816334Z | Info | haskell-language-server version: 2.14.0.0 (GHC: 9.14.1) (PATH: /home/adam/.ghcup/hls/2.14.0.0/lib/haskell-language-server-2.14.0.0/bin/haskell-language-server-9.14.1)
2026-08-26T13:14:06.817247Z | Info | Directory: /home/adam/Documents/Well-Typed/Code/hls-bug
2026-08-26T13:14:06.817538Z | Info | Logging heap statistics every 60.00s
 ghcide setup tester in /home/adam/Documents/Well-Typed/Code/hls-bug.
Report bugs at https://github.com/haskell/haskell-language-server/issues

Step 1/4: Finding files to test in /home/adam/Documents/Well-Typed/Code/hls-bug
2026-08-26T13:14:06.823914Z | Info | Using git to list file, relying on .gitignore
Found 3 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
2026-08-26T13:14:06.830831Z | Info | Cradle path: src-b/B.hs
2026-08-26T13:14:06.831971Z | Warning | No [cradle](https://github.com/mpickering/hie-bios#hie-bios) found for src-b/B.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.
2026-08-26T13:14:06.835849Z | Info | invoking build tool to determine build flags (this may take some time depending on the cache)
2026-08-26T13:14:06.895566Z | Info | Load cabal cradle using single file
2026-08-26T13:14:06.896878Z | Info | cabal --builddir=/home/adam/.cache/hie-bios/dist-hls-bug-9e0fe59a9b659bf2c06b27ac4ecca845 v2-repl --keep-temp-files --with-repl /home/adam/.cache/hie-bios/repl-wrapper-fae20739a232ed1b9dcdf40eca9cf71e /home/adam/Documents/Well-Typed/Code/hls-bug/src-b/B.hs
  Environment Variables
    HIE_BIOS_OUTPUT: /tmp/HIE_BIOS_OUTPUT2847179-0
2026-08-26T13:14:11.431094Z | Info | Interface files cache directory: /home/adam/.cache/ghcide/hls-bug-0.1.0.0-inplace-a1f816539abe5d7f73bac38abe44a3a2012c2d64
2026-08-26T13:14:11.436007Z | Info | Making new HscEnv. In-place unit ids: [hls-bug-0.1.0.0-inplace]
2026-08-26T13:14:11.507308Z | Info | New loaded files: [/home/adam/Documents/Well-Typed/Code/hls-bug/src-b/B.hs]
2026-08-26T13:14:11.508557Z | Info | Cradle path: src-a/A.hs
2026-08-26T13:14:11.508650Z | Warning | No [cradle](https://github.com/mpickering/hie-bios#hie-bios) found for src-a/A.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.
2026-08-26T13:14:11.509928Z | Info | invoking build tool to determine build flags (this may take some time depending on the cache)

2026-08-26T13:14:11.610015Z | Info | Load cabal cradle using single file
2026-08-26T13:14:11.615635Z | Info | cabal --builddir=/home/adam/.cache/hie-bios/dist-hls-bug-9e0fe59a9b659bf2c06b27ac4ecca845 v2-repl --keep-temp-files --with-repl /home/adam/.cache/hie-bios/repl-wrapper-fae20739a232ed1b9dcdf40eca9cf71e /home/adam/Documents/Well-Typed/Code/hls-bug/src-a/A.hs
  Environment Variables
    HIE_BIOS_OUTPUT: /tmp/HIE_BIOS_OUTPUT2847179-1
2026-08-26T13:14:13.592427Z | Info | Interface files cache directory: /home/adam/.cache/ghcide/hls-bug-0.1.0.0-inplace-comp-a-1bae43b96139f751f1ec3f56b6350bf9fbd0ddb9
2026-08-26T13:14:13.592531Z | Info | Interface files cache directory: /home/adam/.cache/ghcide/hls-bug-0.1.0.0-inplace-1bae43b96139f751f1ec3f56b6350bf9fbd0ddb9
2026-08-26T13:14:13.594463Z | Info | Making new HscEnv. In-place unit ids: [ hls-bug-0.1.0.0-inplace
                                      , hls-bug-0.1.0.0-inplace-comp-a ]
2026-08-26T13:14:13.742935Z | Info | New loaded files: [ /home/adam/Documents/Well-Typed/Code/hls-bug/src-a/A2.hs
                  , /home/adam/Documents/Well-Typed/Code/hls-bug/src-a/A.hs ]

Completed (3 files worked, 0 files failed)

[adamgundry]

I forgot to mention: in the original project I also sometimes see errors involving the same modules/definitions of the form

(GetLinkable,NormalizedFilePath "/path/to/Module.hs")IOEnv failure

accompanied by a message in the VSCode log

typecheckCoreFile:
  foo ErrorWithoutFlag
                                    Can't find interface-file declaration for variable foo
                                      Probable cause: bug in .hi-boot file, or inconsistent .hi file
                                      Use -ddump-if-trace to get an idea of which file caused the error

Unfortunately I haven't been able to reproduce this in a minimized example. I'm not sure if it is another manifestation of the same bug.

[wz1000]

I suspect things will be better if you enable multi component loading, in your LSP settings, something like "sessionLoading":"multi"

[crtschin]

Thanks for the minimal reproducer! There was a long-standing hard to spot bug in how we detected transitive reverse dependencies in modules, see #4946, which will be in the next release. This might be fixed on master. I tried checking out the reproducer and running HLS@master against it, and I couldn't get it to reproduce. I could reproduce with HLS@2.14

[adamgundry]

I suspect things will be better if you enable multi component loading, in your LSP settings, something like "sessionLoading":"multi"

I should have mentioned, I've been trying this (as well as single-component).

But indeed, I hadn't tried the latest master, and my minimal example seems to be fine on ce4aabf, so this is definitely better. Thanks very much @crtschin.

Unfortunately, the full project still seems to have problems loading the same modules. Specifically I get the error

Rule execution aborted due to exception

Rule: GetLinkable
Target: /path/to/Module.hs
Message: IOEnv failure
Context:
IPE backtrace:
HasCallStack backtrace:
  throwIO, called at compiler/GHC/Data/IOEnv.hs:108:23 in ghc-9.14.1-3f81:GHC.Data.IOEnv

along with the typecheckCoreFile message quoted above. I'll try to boil this down to a minimal reproducer.

[fendor]

Recompiling HLS with ipe information might give us a better IPE backtrace.

[adamgundry]

Recompiling HLS with ipe information might give us a better IPE backtrace.

Of course since I did that, the Heisenbug has mysteriously vanished. 🤦

I did get a bunch of transient errors like the following (but on different modules, not all of which use TH). This looks like #4721, although I'm not using the eval plugin. Sorry, I realise this is not the most helpful...

Rule execution aborted due to exception

Rule: GetLinkable
Target: /path/to/Module.hs
Message: called GetLinkable for a file without a linkable: NormalizedFilePath "/path/to/Module.hs"
Context:
IPE backtrace:
  Development.IDE.Graph.Internal.Action. (:)
  Development.IDE.Core.Shake.>>= (src/Development/IDE/Graph/Internal/Types.hs:71:23-27)
  UnliftIO.Exception.bracket (src/UnliftIO/Exception.hs:346:25-47)
  UnliftIO.Exception.bracket (src/UnliftIO/Exception.hs:346:3-47)
  Development.IDE.Graph.Internal.Rules.>>= (src/Development/IDE/Graph/Internal/Types.hs:71:23-27)
  Development.IDE.Graph.Internal.Database.compute (src/Development/IDE/Graph/Internal/Database.hs:(189,5)-(190,70))
  Control.Concurrent.Async.Internal.debugLabelMe (./Control/Concurrent/Async/Internal.hs:(959,1)-(963,9))
  Control.Concurrent.Async.Internal.asyncUsing (./Control/Concurrent/Async/Internal.hs:155:20-74)
HasCallStack backtrace:
  error, called at src/Development/IDE/Core/Rules.hs:1245:18 in ghcide-2.14.0.0-7286ee5e0cc582f9e4ccfab84348f02052c87cd46cb532a437f09b8992211617:Development.IDE.Core.Rules

[adamgundry]

I spoke too soon, here's an IPE backtrace of the original TH-related error:

Rule execution aborted due to exception

Rule: GetLinkable
Target: /path/to/Module.hs
Message: IOEnv failure
Context:
IPE backtrace:
  Development.IDE.Core.Compile.coreFileToCgGuts (src/Development/IDE/Core/Compile.hs:1707:81-89)
  Development.IDE.Core.Rules.getLinkableRule (src/Development/IDE/Core/Rules.hs:1288:102-109)
  Development.IDE.Core.Shake.defineEarlyCutoff' (src/Development/IDE/Core/Shake.hs:1311:37-42)
  Development.IDE.Core.Shake.>>= (src/Development/IDE/Graph/Internal/Types.hs:71:23-27)
  UnliftIO.Exception.bracket (src/UnliftIO/Exception.hs:346:25-47)
  UnliftIO.Exception.bracket (src/UnliftIO/Exception.hs:346:3-47)
  Development.IDE.Graph.Internal.Rules.>>= (src/Development/IDE/Graph/Internal/Types.hs:71:23-27)
  Development.IDE.Graph.Internal.Database.compute (src/Development/IDE/Graph/Internal/Database.hs:(189,5)-(190,70))
  Control.Concurrent.Async.Internal.debugLabelMe (./Control/Concurrent/Async/Internal.hs:(959,1)-(963,9))
  Control.Concurrent.Async.Internal.asyncUsing (./Control/Concurrent/Async/Internal.hs:155:20-74)
HasCallStack backtrace:
  throwIO, called at compiler/GHC/Data/IOEnv.hs:108:23 in ghc-9.14.1-3f81:GHC.Data.IOEnv