haskell-mode not able to find GHC installation

Question

I installed haskell-mode and I want to launch the REPL GHCi with the command C-c C-z.

However, on typing C-c C-z, it shows error Could not find any installation of GHC.

And when I use same command again, it launches a new window with what looks like ghci. But when I try to type and execute something, it shows an error "haskell-process" has died as below. (If it matters at all, there is a tests.cabal in the directory where the current open file resides)

If I enter y then it throws the same error as above about GHC not being found.

Now I have my GHC, Stack, Cabal, and HLS installations managed through GHCup. Therefore by default, I only have the ghcup path in the system PATH variable.

Since many places online said that there needs to be the ghc path in the PATH, I added the line export PATH=$PATH:/home/axiom/.ghcup/bin/ghc to my .bashrc. But this didn't fix anything.

Further, I looked for other solutions and tried two more things:

I added the following lines in my .emacs.d/init.el :

(setenv "PATH" (concat "/home/axiom/.ghcup/bin/ghc" (getenv "PATH")))
(setq exec-path (append '("/home/axiom/.ghcup/bin/ghc") exec-path))

Adding this also didn't solve anything.

Then I replaced the above lines with (setq haskell-process-path-ghci "/home/axiom/.ghcup/bin/ghc") and this didn't help either.

I think the error Could not find any installation of GHC. is being returned from a piece of code in this file https://github.com/haskell/haskell-mode/blob/master/haskell-customize.el but I am not able to figure out how to fix my system according to what the haskell-mode code is trying to do before throwing the above error.

Answer 1

I had the same issue after switching to ghcup.

As the comments pointed out, using directories to ghci rather than the executable itself solves the problem:

(let ((my-ghcup-path (expand-file-name "~/.ghcup/bin")))
  (setenv "PATH" (concat my-ghcup-path ":" (getenv "PATH")))
  (add-to-list 'exec-path my-ghcup-path))

(tested under Ubuntu 22.04)

Answer 2

Yeah, the tinlyx's solution also works on my MacBook Air M1 with Emacs installed with homebrew (specifically GNU Emacs 29.4 (build 1, aarch64-apple-darwin21.6.0, NS appkit-2113.60 Version 12.6.6 (Build 21G646)) of 2024-08-03) And GHC(i) from GHCup.