Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] next goal: pandoc-citeproc (user goal)
[__0] rejecting: pandoc-citeproc-0.17.0.2, pandoc-citeproc-0.17.0.1,
pandoc-citeproc-0.17, pandoc-citeproc-0.16.4.1, pandoc-citeproc-0.16.4
(constraint from user target requires ==0.16.3.1)
[__0] trying: pandoc-citeproc-0.16.3.1
[__1] next goal: pandoc-types (dependency of pandoc-citeproc)
[__1] rejecting: pandoc-types-1.22 (conflict: pandoc-citeproc =>
pandoc-types>=1.17.3 && <1.18)
[__1] skipping: pandoc-types-1.21, pandoc-types-1.20 (has the same
characteristics that caused the previous version to fail: excluded by
constraint '>=1.17.3 && <1.18' from 'pandoc-citeproc')
[__1] trying: pandoc-types-1.17.6.1
[__2] next goal: pandoc (dependency of pandoc-citeproc)
[__2] rejecting: pandoc-2.11.0.4 (conflict: pandoc-citeproc => pandoc>=1.16 &&
<2.9)
[__2] skipping: pandoc-2.11.0.2, pandoc-2.11.0.1, pandoc-2.11, pandoc-2.10.1,
pandoc-2.10, pandoc-2.9.2.1, pandoc-2.9.2, pandoc-2.9.1.1, pandoc-2.9.1,
pandoc-2.9 (has the same characteristics that caused the previous version to
fail: excluded by constraint '>=1.16 && <2.9' from 'pandoc-citeproc')
[__2] rejecting: pandoc-2.8.1 (conflict: pandoc-types==1.17.6.1, pandoc =>
pandoc-types>=1.20 && <1.21)
[__2] skipping: pandoc-2.8.0.1, pandoc-2.8 (has the same characteristics that
caused the previous version to fail: excludes 'pandoc-types' version 1.17.6.1)
[__2] trying: pandoc-2.7.3
[__3] next goal: haddock-library (dependency of pandoc)
[__3] rejecting: haddock-library-1.9.0 (conflict: pandoc =>
haddock-library>=1.7 && <1.8)
[__3] skipping: haddock-library-1.8.0 (has the same characteristics that
caused the previous version to fail: excluded by constraint '>=1.7 && <1.8'
from 'pandoc')
[__3] trying: haddock-library-1.7.0
[__4] next goal: base (dependency of pandoc-citeproc)
[__4] rejecting: base-4.14.1.0/installed-4.14.1.0 (conflict: haddock-library
=> base>=4.5 && <4.13)
[__4] skipping: base-4.14.0.0, base-4.13.0.0 (has the same characteristics
that caused the previous version to fail: excluded by constraint '>=4.5 &&
<4.13' from 'haddock-library')
[__4] rejecting: 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)
[__4] fail (backjumping, conflict set: base, haddock-library, pandoc-citeproc)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: pandoc, pandoc-citeproc, pandoc-types,
base, haddock-library
Try running with --minimize-conflict-set to improve the error message.