Adding `{-# OPTIONS_GHC -Wno-all #-}` at the top of the file makes HLS cease to report errors, not only warnings.

[kindaro]

Your environment

Which OS do you use? ArchLinux.

Which version of GHC do you use and how did you install it? 9.4.8, via ghcup.

How is your project built (alternative: link to the project)? With Cabal.

Which LSP client (editor/plugin) do you use? emacs and lsp-mode.

Which version of HLS do you use and how did you install it? 2.5.0.0, 2.7.0.0, 2.9.0.1, via ghcup.

Have you configured HLS in any way (especially: a hie.yaml file)? No. gen-hie > hie.yaml has no effect.

Steps to reproduce

Create a file like so:

{-# OPTIONS_GHC -Wno-all  #-}

module Example where

f :: Int
f = g

Run haskell-language-server-wrapper Example.hs.

Expected behaviour

g is not in scope; GHC could not compile this file. HLS should show this error to me in the editor and when running from the command line.

Actual behaviour

HLS does not report the error.

Debug information

https://gist.github.com/kindaro/23d8232be484cdd8b650617709d7f355

[fendor]

Hi, thank you for your bug report!

I think this is likely an interaction with -fdefer-type-errors, e.g.

> ghc -fdefer-type-errors Example.hs
[1 of 1] Compiling Example          ( Example.hs, Example.o ) [Source file changed]

I don't think there is much we can do about that.

A potential remedy could be: https://gitlab.haskell.org/ghc/ghc/-/issues/24329