vincenthz
Build error - ‘fail’ is not a (visible) method of class ‘Monad’
I created a test project with stack new git-test simple.
I then added the git to my project cabal file, and an entry in stack.yaml so the package could be used:
extra-deps:
- git-0.3.0@sha256:dc070840ab24792c9664b9e3e69c9d55d30fc36fee41049c548bb0e8ec83c919,3448
stack build then fails with:
git > /run/user/1020/stack-d922b28e78b92425/git-0.3.0/Data/Git/Monad.hs:243:5: error:
git > ‘fail’ is not a (visible) method of class ‘Monad’
git > |
git > 243 | fail = failGitM
git > | ^^^^
git >
git > /run/user/1020/stack-d922b28e78b92425/git-0.3.0/Data/Git/Monad.hs:316:5: error:
git > ‘fail’ is not a (visible) method of class ‘Monad’
git > |
git > 316 | fail = failCommitAccessM
git > | ^^^^
git >
git > /run/user/1020/stack-d922b28e78b92425/git-0.3.0/Data/Git/Monad.hs:477:5: error:
git > ‘fail’ is not a (visible) method of class ‘Monad’
git > |
git > 477 | fail = failCommitM
git > | ^^^^
Am I doing something obviously incorrect?
https://gitlab.haskell.org/ghc/ghc/-/issues/16849 seems related.
That makes me wonder if the fix is to update this package to either use/include an instance when it's missing from GHC, or to skip that, when the GHC version has it, but IDK if that is even the right thing to do here (nor how to do it).
I'm learning more about this topic here - https://github.com/quchen/articles/blob/master/monad_fail.md - thanks to @norfairking for the pointer.
After some digging, I see that 0.3.0 is the "latest" release, except it's quite old, and there have been a couple updates since then. I believe this would be resolved with a new version being tagged/released.
The underlying issue was resolved in #18, but that hasn't been been released, so users who see 0.3.0 on hackage will run into this issue with current GHC versions and stackage LTS. I've created #24 for that.