The import of ‘Control.Applicative’ is redundant - when using GHC 7.10

[nikomi]

Maybe this has already been solved but not yet found its way to hackage:

When compiling modules created by Alex 3.1.4 with GHC 7.10.2 the following warning comes up:

templates/wrappers.hs:7:1: Warning:
    The import of ‘Control.Applicative’ is redundant
      except perhaps to import instances from ‘Control.Applicative’
    To import instances alone, use: import Control.Applicative()

I'm using Alex 3.1.4 - the newest I could find on hackage:

$ alex --version
Alex version 3.1.4, (c) 2003 Chris Dornan and Simon Marlow

I think this is one of the topics covered in https://ghc.haskell.org/trac/ghc/wiki/Migration/7.10

thx, nikomi

[chamini2]

I think this is already solved with pull request #69

[nikomi]

Thanx for the info!

Now it's just a matter of time until this will show up on hackage :-)

[nikomi]

Now I'm a bit confused - after reading the change history

Changes in 3.1.5:

Generate less warning-laden code, and suppress other warnings.

I installed the newest Alex 3.1.6

$ alex --version
Alex version 3.1.6, (c) 2003 Chris Dornan and Simon Marlow

and now I see even more warnings:

templates/wrappers.hs:7:1: Warning:
    The import of ‘Control.Applicative’ is redundant
      except perhaps to import instances from ‘Control.Applicative’
    To import instances alone, use: import Control.Applicative()

templates/wrappers.hs:8:1: Warning:
    The qualified import of ‘Control.Monad’ is redundant
      except perhaps to import instances from ‘Control.Monad’
    To import instances alone, use: import Control.Monad()

templates/wrappers.hs:10:1: Warning:
    The import of ‘Data.Int’ is redundant
      except perhaps to import instances from ‘Data.Int’
    To import instances alone, use: import Data.Int()

What am I doing wrong? Did the perhaps the templates get mixed up?

[hvr]

@nikomi can you test whether this has improved with the just released alex-3.1.7?

[nikomi]

It has - only one warning left:

templates/wrappers.hs:9:1: Warning:
    The qualified import of ‘Control.Monad’ is redundant
      except perhaps to import instances from ‘Control.Monad’
    To import instances alone, use: import Control.Monad()

[hvr]

...at least we're getting closer =)

I've some vague plans to improve alex' testsuite to help detect this...

[nikomi]

Great!

Thanx for taking care!

[josephcsible]

@nikomi That should be fixed by #134.

[andreasabel]

Shouldn't this issue be closed?

There are similar problems, of course, on 8.4.4 we get the warning

[ 3 of 22] Compiling Data.Ranged.RangedSet
src/Data/Ranged/RangedSet.hs:31:1: warning: [-Wunused-imports]
    The import of ‘Data.Semigroup’ is redundant
      except perhaps to import instances from ‘Data.Semigroup’
    To import instances alone, use: import Data.Semigroup()
   |
31 | import Data.Semigroup
   | ^^^^^^^^^^^^^^^^^^^^^

but this isn't the original issue.

[simonmar]

It would be good to make Alex -Wall clean, but no need to have this issue I think.