Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: Hs2lib (user goal)
rejecting: Hs2lib-0.6.3, Hs2lib-0.6.1, Hs2lib-0.6.0, Hs2lib-0.5.6 (constraint
from user target requires ==0.5.5)
trying: Hs2lib-0.5.5
next goal: ghc-boot (dependency of haddock-api-2.17.3)
rejecting: ghc-boot-8.0.1.20161018/installed-8.0... (conflict: ghc-boot =>
filepath==1.4.1.0/installed-1.4..., Hs2lib => filepath>=1 && <1.3)
trying: ghc-boot-8.0.1
next goal: filepath (dependency of Hs2lib-0.5.5)
rejecting: filepath-1.4.1.0/installed-1.4..., filepath-1.4.1.1,
filepath-1.4.1.0, filepath-1.4.0.0, filepath-1.3.0.2, filepath-1.3.0.1,
filepath-1.3.0.0 (conflict: Hs2lib => filepath>=1 && <1.3)
rejecting: filepath-1.2.0.1, filepath-1.2.0.0, filepath-1.1.0.4,
filepath-1.1.0.3, filepath-1.1.0.2 (conflict: ghc-boot => filepath>=1.3 &&
<1.5)
rejecting: filepath-1.1.0.1, filepath-1.1.0.0, filepath-1.0 (conflict: Hs2lib
=> filepath>=1.1.0.2)
Dependency tree exhaustively searched.