Thank you all. Did not know I should update cabal as well.

'ghc-pkg dump' error was just because I forgot to initialize database.

Magicloud Magiclouds <magicloud.magiclouds@gmail.com>于2016年7月11日周一下午3:49写道：

Hi,
I update my GHC to 8.0.1 and failed to install any packages since then.
If I use cabal, I got 'installed package info from too old version of Cabal (key field does not match id field)' for every package.
If I use Setup.hs, I got 'Configuring Cabal-1.24.0.0...
Setup.hs: ghc-pkg dump failed'.
What should I do? Googling did not get me an answer.