Resolving dependencies...
Downloading ip6addr-0.3.1...
Configuring ip6addr-0.3.1...
Building ip6addr-0.3.1...
Preprocessing executable 'ip6addrcan' for ip6addr-0.3.1...
[1 of 3] Compiling CidrSuffix       ( src/CidrSuffix.hs, dist/build/ip6addrcan/ip6addrcan-tmp/CidrSuffix.o )
[2 of 3] Compiling IPv6Addr         ( src/IPv6Addr.hs, dist/build/ip6addrcan/ip6addrcan-tmp/IPv6Addr.o )

src/IPv6Addr.hs:217:36:
    Could not deduce (Eq b) arising from a use of `/='
    from the context (Num b)
      bound by the type signature for
                 firstLongestZerosRunIndex :: Num b => [(Bool, b)] -> b -> b
      at src/IPv6Addr.hs:215:30-61
    Possible fix:
      add (Eq b) to the context of
        the type signature for
          firstLongestZerosRunIndex :: Num b => [(Bool, b)] -> b -> b
    In the first argument of `takeWhile', namely `(/= (True, y))'
    In the second argument of `($)', namely
      `takeWhile (/= (True, y)) x'
    In the expression: sum . snd . unzip $ takeWhile (/= (True, y)) x
Failed to install ip6addr-0.3.1
cabal: Error: some packages failed to install:
ip6addr-0.3.1 failed during the building phase. The exception was:
ExitFailure 1