Bump mtl and transformer bounds (fixes #8144)

[Mikolaj]

Fixes #8144.

[Mikolaj]

[Edit: we managed to find an error, so let's put this on hold until the ecosystem catches up or we manage to determine additional deps to bump. See comments below.]

Anybody? If nobody wants to review, I'd just merge, because there is not much to review and the changes probably don't have any effect until GHC 9.4 and won't show in CI until hackage-security is updated, anyway.

[fgaz]

Does it at least build with appropriate --constraint and --allow-newer flags?

[Mikolaj]

@fgaz: you were right, this was worth trying and we did get an early error:

I tried cabal build --project-file=cabal.project.mine cabal-install --constraint "transformers >=0.6" --constraint "mtl >=2.3" --allow-newer --constraint "happy >=1.21.0" and it seems I can't transitively constrain happy that is used as a tool in another package (one of the test harnesses, probably) (and I'm not sure happy 1.21 would compile, but worth trying):

Building executable 'happy' for happy-1.20.0..
[ 1 of 19] Compiling AbsSyn           ( src/AbsSyn.lhs, dist/build/happy/happy-tmp/AbsSyn.o )
[ 2 of 19] Compiling GenUtils         ( src/GenUtils.lhs, dist/build/happy/happy-tmp/GenUtils.o )
[ 3 of 19] Compiling NameSet          ( src/NameSet.hs, dist/build/happy/happy-tmp/NameSet.o )
[ 4 of 19] Compiling ParamRules       ( src/ParamRules.hs, dist/build/happy/happy-tmp/ParamRules.o )

src/ParamRules.hs:41:17: error:
    Not in scope: type constructor or class ‘ExceptT’
   |
41 | type M2       = ExceptT String M1
   |                 ^^^^^^^

src/ParamRules.hs:81:10: error:
    Not in scope: type constructor or class ‘ExceptT’
   |
81 | runM2 :: ExceptT e (Writer w) a -> Either e (a, w)
   |          ^^^^^^^
Error: cabal: Failed to build exe:happy from happy-1.20.0 (which is required
by test:long-tests from cabal-install-3.7.0.0). See the build log above for
details.

[Mikolaj]

Any help would be welcome, BTW. :)

[andreasabel]

The export of ExceptT is missing from mtl-2.3 in error:

• mtl-2.3 dropped ExceptT mtl#117
• Restore ExceptT re-exports mtl#121

I expect a patch on hackage soon.

The idea that testing with mtl-2.3 RC3 should be sufficient to go through with mtl-2.3, but this is now not true. Hopefully with the patched version.

[Mikolaj]

Wow, good to know. Thanks.

[ulysses4ever]

Is there a plan for this? What is it waiting for?

[Mikolaj]

It was waiting for a fix to mtl. Is is it ready now?

[ulysses4ever]

Right… I was under the impression that the patch was out (and it was), but it turned out that there’s no release yet… Okay, waiting some more.

[Mikolaj]

@mergify rebase

[mergify]

rebase

✅ Branch has been successfully rebased

[Mikolaj]

Apparently, happy has been changed not to use the new broken mtl and so compiles fine (using the old mtl) and now have some new errors. The errors for hackage-security are expected and should vanish once mtl is fixed, but the other set seems unrelated and worth investigating if somebody has moment.

~/r/cabal$ cabal build --project-file=cabal.project.mine cabal-install --constraint "transformers >=0.6" --constraint "mtl >=2.3" --allow-newer --constraint "happy >=1.21.0"
Resolving dependencies...
Build profile: -w ghc-9.2.3 -O0
In order, the following will be built (use -v for more details):
 - transformers-0.6.0.4 (lib) (requires build)
 - mtl-2.3 (lib) (requires build)
 - random-1.2.1.1 (lib) (requires build)
 - parsec-3.1.15.1 (lib) (requires build)
 - exceptions-0.10.5 (lib) (requires build)
 - edit-distance-0.2.2.1 (lib) (requires build)
 - network-uri-2.6.4.1 (lib) (requires build)
 - Cabal-syntax-3.7.0.0 (lib) (first run)
 - safe-exceptions-0.1.7.3 (lib) (requires build)
 - HTTP-4000.4.1 (lib) (requires build)
 - Cabal-3.7.0.0 (lib) (first run)
 - hackage-security-0.6.2.1 (lib) (configuration changed)
 - cabal-install-solver-3.7.0.0 (lib) (first run)
 - cabal-install-3.7.0.0 (lib) (first run)
 - cabal-install-3.7.0.0 (exe:cabal) (first run)
Starting     transformers-0.6.0.4 (lib)
...
[ 9 of 43] Compiling Hackage.Security.Util.Exit ( src/Hackage/Security/Util/Exit.hs, /home/mikolaj/r/cabal/dist-newstyle/build/x86_64-linux/ghc-9.2.3/hackage-security-0.6.2.1/build/Hackage/Security/Util/Exit.o, /home/mikolaj/r/cabal/dist-newstyle/build/x86_64-linux/ghc-9.2.3/hackage-security-0.6.2.1/build/Hackage/Security/Util/Exit.dyn_o ) [Control.Monad.Except changed]

src/Hackage/Security/Util/Exit.hs:32:34: error:
    Not in scope: type constructor or class ‘ExceptT’
   |
32 | multipleExitPoints :: Monad m => ExceptT a m a -> m a
   |                                  ^^^^^^^

src/Hackage/Security/Util/Exit.hs:40:25: error:
    Not in scope: type constructor or class ‘ExceptT’
   |
40 | exit :: Monad m => e -> ExceptT e m a
   |                         ^^^^^^^
...
[28 of 50] Compiling Distribution.Solver.Modular.Linking ( src/Distribution/Solver/Modular/Linking.hs, /home/mikolaj/r/cabal/dist-newstyle/build/x86_64-linux/ghc-9.2.3/cabal-install-solver-3.7.0.0/noopt/build/Distribution/Solver/Modular/Linking.o, /home/mikolaj/r/cabal/dist-newstyle/build/x86_64-linux/ghc-9.2.3/cabal-install-solver-3.7.0.0/noopt/build/Distribution/Solver/Modular/Linking.dyn_o )

src/Distribution/Solver/Modular/Linking.hs:245:10: error:
    • Variable not in scope:
        zipWithM_
          :: (FlaggedDep QPN -> FlaggedDep QPN -> UpdateState ())
             -> FlaggedDeps QPN -> FlaggedDeps QPN -> UpdateState ()
    • Perhaps you meant one of these:
        ‘zipWith’ (imported from Distribution.Solver.Compat.Prelude),
        ‘zipWith3’ (imported from Distribution.Solver.Compat.Prelude)
    |
245 |     go = zipWithM_ go1
    |          ^^^^^^^^^

src/Distribution/Solver/Modular/Linking.hs:306:5: error:
    • Variable not in scope:
        forM_
          :: [PackagePath]
             -> (PackagePath -> UpdateState ()) -> UpdateState ()
    • Perhaps you meant one of these:
        ‘for_’ (imported from Distribution.Solver.Compat.Prelude),
        ‘T.forM’ (imported from Data.Traversable)
    |
306 |     forM_ (S.toList linkedTo) $ \pp' -> linkDeps (Q pp' pn) newDeps
    |     ^^^^^

src/Distribution/Solver/Modular/Linking.hs:353:9: error:
    • Variable not in scope:
        forM_ :: [Flag] -> (Flag -> UpdateState ()) -> UpdateState a0
    • Perhaps you meant one of these:
        ‘for_’ (imported from Distribution.Solver.Compat.Prelude),
        ‘T.forM’ (imported from Data.Traversable)
    |
353 |         forM_ flags $ \fn -> do
    |         ^^^^^

src/Distribution/Solver/Modular/Linking.hs:356:9: error:
    • Variable not in scope:
        forM_
          :: [OptionalStanza] -> (Stanza -> UpdateState ()) -> UpdateState ()
    • Perhaps you meant one of these:
        ‘for_’ (imported from Distribution.Solver.Compat.Prelude),
        ‘T.forM’ (imported from Data.Traversable)
    |
356 |         forM_ stanzas $ \sn -> do
    |         ^^^^^

[andreasabel]

The way to fix the errors not involving ExceptT, e.g.

• Variable not in scope:
zipWithM_

is to add import Control.Monad but then also import from the mtl modules Control.Monad.* explicitly, so as to avoid annoying unused-import warnings when built with mtl < 2.3.

[Mikolaj]

Fixed in #8610.