slackbuilds/haskell/haskell-transformers-compat/README

This package includes backported versions of types that were added to
transformers in transformers 0.3 and 0.4 for users who need strict
transformers 0.2 or 0.3 compatibility to run on old versions of the
platform, but also need those types.

After uninstalling, run this command to unregister the package from
the ghc package database:   ghc-pkg recache