Type error in one file, only after opening other.

[lsmor]

Your environment

• OS: Ubuntu
• ghc-9.2.8 from ghcup
• The project is current master branch of ghcup tool. (commit: a73ce18)
• vscode; haskell extension
• bug reproduced with hls-2.1.0.0 and 2.3.0.0

# hie.yaml
cradle:
  cabal:
  - component: "ghcup:lib:ghcup"
    path: ./lib
  - component: "ghcup:exe:ghcup"
    path: ./app/ghcup
  - component: "ghcup:test:ghcup-test"
    path: ./test/ghcup-test
  - component: "ghcup:test:ghcup-optparse-test"
    path: ./test/optparse-test

Steps to reproduce

1. Clone ghcup repo (commit at the time of writting this: a73ce18)
2. Open app/BrickMain.hs file in the editor (vscode in my case)
3. Wait until hls finishes compiling/indexing etc... and stays idle
4. Without closing BrickMain.hs open lib/Types.hs (the file not the folder)

Expected behaviour

Nothing should happen other than listing / processing / indexing files.

Actual behaviour

Suddenly, file BrickMain.hs shows a type error in line 577. Very rare since the project does compile perfectly with cabal

[fendor]

Hi!

Without checking too thoroughly, my gut tells me this is related to #3738. It is usually the culprit for such errors.

[fendor]

I can reproduce and the issue is caused by #3738. Essentially, you have to make sure maintain the closure property of home units, see https://gitlab.haskell.org/ghc/ghc/-/blob/master/compiler/GHC/Unit/Env.hs#L548.

Make you sure you open all components in the ghcup project in your project to fix this or wait for #3738. Closing this in favour of #3738 which tracks our efforts to fix these kinds of issues.