Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: sequent-core (user goal)
rejecting: sequent-core-0.5.0.1 (constraint from user target requires ==0.5)
trying: sequent-core-0.5
next goal: ghc (dependency of sequent-core-0.5)
rejecting: ghc-8.0.1.20161018/installed-8.0... (conflict: sequent-core =>
ghc>=7.8 && <7.10)
Dependency tree exhaustively searched.