smallcheck-1.1.1 doesn't compile with current GHC head snapshot

[peti]

Citing from http://hydra.cryp.to/build/794575/nixlog/13/raw:

Test/SmallCheck/Property.hs:187:10:
    Could not deduce (Monad n)
      arising from the superclasses of an instance declaration
    from the context: (Monad m, m ~ n)
      bound by the instance declaration
      at Test/SmallCheck/Property.hs:187:10-52
    Possible fix:
      add (Monad n) to the context of the instance declaration
    In the instance declaration for ‘Testable n (Property m)’

[UnkindPartition]

Reported as a ghc regression: https://ghc.haskell.org/trac/ghc/ticket/10423

[UnkindPartition]

Should be fixed in ghc now.