Resolving dependencies...
Error: cabal: Could not resolve dependencies:
[__0] next goal: haddock-api (user goal)
[__0] rejecting: haddock-api-2.27.0 (constraint from user target requires
==2.26.0)
[__0] trying: haddock-api-2.26.0
[__1] next goal: haddock-library (dependency of haddock-api)
[__1] rejecting: haddock-library-1.11.0 (conflict: haddock-api =>
haddock-library^>=1.9.0)
[__1] skipping: haddock-library-1.10.0 (has the same characteristics that
caused the previous version to fail: excluded by constraint '^>=1.9.0' from
'haddock-api')
[__1] trying: haddock-library-1.9.0
[__2] next goal: base (dependency of haddock-api)
[__2] rejecting: base-4.16.3.0/installed-4.16.3.0 (conflict: haddock-library
=> base>=4.5 && <4.15)
[__2] skipping: base-4.17.0.0, base-4.16.4.0, base-4.16.3.0, base-4.16.2.0,
base-4.16.1.0, base-4.16.0.0, base-4.15.1.0, base-4.15.0.0 (has the same
characteristics that caused the previous version to fail: excluded by
constraint '>=4.5 && <4.15' from 'haddock-library')
[__2] rejecting: base-4.14.3.0, base-4.14.2.0, 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, 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)
[__2] fail (backjumping, conflict set: base, haddock-api, haddock-library)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: base, haddock-api, haddock-library