cabal install cabal-install could not resolve dependencies

Question

I just did brew install haskell-platform and it installed The Glorious Glasgow Haskell Compilation System, version 7.6.3 .

$ cabal --version
cabal-install version 1.16.0.2
using version 1.16.0 of the Cabal library

$ cabal update
Downloading the latest package list from hackage.haskell.org
Note: there is a new version of cabal-install available.
To upgrade, run: cabal install cabal-install

$ cabal install cabal-install
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: cabal-install-1.20.0.3
rejecting: zlib-0.5.4.1, 0.5.4.0, 0.5.3.3, 0.5.3.2, 0.5.3.1, 0.5.2.0, 0.5.0.0,
0.4.0.4, 0.4.0.3, 0.4.0.2, 0.4.0.1, 0.4, 0.3, 0.2 (global constraint requires 
installed instance)

I don't understand what the problem is here, I just installed everything for the first time.

Answer 1

I just had a bad ~/.cabal/config file before installing.

I did

$ rm -rf ~/.ghc ~/.cabal
$ brew rm ghc 
$ brew rm haskell-platform
$ brew install haskell-platform

and it installed OK

$ cabal install cabal-install
Resolving dependencies...
Downloading Cabal-1.20.0.2...
...