Compile fail with GHC HEAD

[snoyberg]

I get the following error message when using the newest GHC HEAD:

Network/BufferType.hs:57:10:
    Illegal instance declaration for ‛BufferType String’
      (All instance types must be of the form (T a1 ... an)
       where a1 ... an are *distinct type variables*,
       and each type variable appears at most once in the instance head.
       Use -XFlexibleInstances if you want to disable this.)
    In the instance declaration for ‛BufferType String’
Failed to install HTTP-4000.0.7

[23Skidoo]

4000.2.8 compiles fine for me with GHC 7.7.20130720.

[juhp]

base needs a version bump now as of 7.7.20130828

I opened a pull request for this in issue 46.

[Fuuzetsu]

Same error with The Glorious Glasgow Haskell Compilation System, version 7.7.20130904 for 4000.2.8

[schell]

I have the same issue, cabal versioning is forcing an attempt to compile 4000.0.7.

[hsenag]

As far as I understand this is fixed or not reproducible in the latest version.

If there's a problem with cabal selecting an old version I'm not sure if there's anything much the HTTP package can do about it.