Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] next goal: haddock (user goal)
[__0] rejecting: haddock-2.25.0, haddock-2.24.2, haddock-2.24.1,
haddock-2.24.0, haddock-2.23.1, haddock-2.23.0, haddock-2.22.0,
haddock-2.21.0, haddock-2.20.0, haddock-2.19.0.1 (constraint from user target
requires ==2.18.1)
[__0] trying: haddock-2.18.1
[__1] next goal: base (dependency of haddock)
[__1] rejecting: base-4.14.1.0/installed-4.14.1.0 (conflict: haddock =>
base>=4.3 && <4.11)
[__1] skipping: base-4.15.0.0, base-4.14.1.0, base-4.14.0.0, base-4.13.0.0,
base-4.12.0.0, base-4.11.1.0, base-4.11.0.0 (has the same characteristics that
caused the previous version to fail: excluded by constraint '>=4.3 && <4.11'
from 'haddock')
[__1] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0,
base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1,
base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0,
base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2,
base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2,
base-3.0.3.1 (constraint from non-upgradeable package requires installed
instance)
[__1] fail (backjumping, conflict set: base, haddock)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: base, haddock