cabal install helm error: ambiguous "pure"

[Jonathan Bush]

My OS is Linux Mint 18. Following the instructions at http://helm-engine.org/guide/installing/
I got as far as

cabal install gtk2hs-buildtools

which installed successfully, but here is what happened next:

$ cabal install helm
Resolving dependencies...
Configuring helm-0.4...
Building helm-0.4...
Failed to install helm-0.4
Build log ( /home/david/.cabal/logs/helm-0.4.log ):
Configuring helm-0.4...
Building helm-0.4...
Preprocessing library helm-0.4...
[ 1 of 12] Compiling FRP.Helm.Window  ( src/FRP/Helm/Window.hs, dist/build/FRP/Helm/Window.o )

src/FRP/Helm/Window.hs:3:1: Warning: Tab character

src/FRP/Helm/Window.hs:4:1: Warning: Tab character

src/FRP/Helm/Window.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()
[ 2 of 12] Compiling FRP.Helm.Mouse   ( src/FRP/Helm/Mouse.hs, dist/build/FRP/Helm/Mouse.o )

src/FRP/Helm/Mouse.hs:11:1: Warning:
    The import of ‘Control.Applicative’ is redundant
      except perhaps to import instances from ‘Control.Applicative’
    To import instances alone, use: import Control.Applicative()
[ 3 of 12] Compiling FRP.Helm.Keyboard ( src/FRP/Helm/Keyboard.hs, dist/build/FRP/Helm/Keyboard.o )

src/FRP/Helm/Keyboard.hs:12:1: Warning:
    The import of ‘Control.Applicative’ is redundant
      except perhaps to import instances from ‘Control.Applicative’
    To import instances alone, use: import Control.Applicative()
[ 4 of 12] Compiling FRP.Helm.Joystick ( src/FRP/Helm/Joystick.hs, dist/build/FRP/Helm/Joystick.o )

src/FRP/Helm/Joystick.hs:21:1: Warning:
    The import of ‘Control.Applicative’ is redundant
      except perhaps to import instances from ‘Control.Applicative’
    To import instances alone, use: import Control.Applicative()
[ 5 of 12] Compiling FRP.Helm.Automaton ( src/FRP/Helm/Automaton.hs, dist/build/FRP/Helm/Automaton.o )

src/FRP/Helm/Automaton.hs:34:9:
    Ambiguous occurrence ‘pure’
    It could refer to either ‘FRP.Helm.Automaton.pure’,
                             defined at src/FRP/Helm/Automaton.hs:40:1
                          or ‘Prelude.pure’,
                             imported from ‘Prelude’ at src/FRP/Helm/Automaton.hs:17:1-31
                             (and originally defined in ‘GHC.Base’)

src/FRP/Helm/Automaton.hs:40:23:
    Ambiguous occurrence ‘pure’
    It could refer to either ‘FRP.Helm.Automaton.pure’,
                             defined at src/FRP/Helm/Automaton.hs:40:1
                          or ‘Prelude.pure’,
                             imported from ‘Prelude’ at src/FRP/Helm/Automaton.hs:17:1-31
                             (and originally defined in ‘GHC.Base’)
cabal: Error: some packages failed to install:
helm-0.4 failed during the building phase. The exception was:
ExitFailure 1

Any clue would be welcome, TIA!

 

[Jonathan Bush]

I finally noticed that Helm 0.4 is deprecated. Sorry, but hey, that's what cabal chose for the "latest stable version."
So, instead, I used the cabal install command to install the latest development version. Attached is the full output, which ends like this:

Preprocessing library helm-0.8.0...
[ 1 of 13] Compiling FRP.Helm.Sample  ( src/FRP/Helm/Sample.hs, dist/build/FRP/Helm/Sample.o )
[ 2 of 13] Compiling FRP.Helm.Utilities ( src/FRP/Helm/Utilities.hs, dist/build/FRP/Helm/Utilities.o )
[ 3 of 13] Compiling FRP.Helm.Engine  ( src/FRP/Helm/Engine.hs, dist/build/FRP/Helm/Engine.o )
[ 4 of 13] Compiling FRP.Helm.Signal  ( src/FRP/Helm/Signal.hs, dist/build/FRP/Helm/Signal.o )
[ 5 of 13] Compiling FRP.Helm.Time    ( src/FRP/Helm/Time.hs, dist/build/FRP/Helm/Time.o )

src/FRP/Helm/Time.hs:26:54:
    Module ‘FRP.Elerea.Param’ does not export ‘until’

cabal: Error: some packages failed to install:

helm-0.8.0 failed during the building phase. The exception was:
ExitFailure 1

Again, clues are much appreciated, TIA