Resolving dependencies...
cabal: Could not resolve dependencies:
trying: formal-0.1.0 (user goal)
trying: directory-1.2.6.2/installed-1.2... (dependency of formal-0.1.0)
next goal: unix (dependency of directory-1.2.6.2/installed-1.2...)
rejecting: unix-2.7.2.0/installed-2.7... (conflict: unix =>
bytestring==0.10.8.1/installed-0.1..., formal => bytestring>=0.9.1 && <0.10)
rejecting: unix-2.7.2.1, unix-2.7.2.0, unix-2.7.1.0, unix-2.7.0.1,
unix-2.7.0.0, unix-2.6.0.1, unix-2.6.0.0, unix-2.5.1.1, unix-2.5.1.0,
unix-2.5.0.0, unix-2.4.2.0, unix-2.4.1.0, unix-2.4.0.2, unix-2.4.0.1,
unix-2.4.0.0, unix-2.3.2.0, unix-2.3.1.0, unix-2.3.0.0, unix-2.2.0.0, unix-2.0
(conflict: directory => unix==2.7.2.0/installed-2.7...)
Dependency tree exhaustively searched.