Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: doctest (user goal)
rejecting: doctest-0.11.0, doctest-0.10.1, doctest-0.10.0, doctest-0.9.13,
doctest-0.9.12, doctest-0.9.11.1, doctest-0.9.11, doctest-0.9.10.2,
doctest-0.9.10.1, doctest-0.9.10, doctest-0.9.9, doctest-0.9.8, doctest-0.9.7,
doctest-0.9.6, doctest-0.9.5.1, doctest-0.9.5, doctest-0.9.4.1, doctest-0.9.4,
doctest-0.9.3, doctest-0.9.2.1, doctest-0.9.2, doctest-0.9.1, doctest-0.9.0,
doctest-0.8.0.1, doctest-0.8.0, doctest-0.7.0, doctest-0.6.1, doctest-0.6.0.1,
doctest-0.6.0 (constraint from user target requires ==0.5.2)
trying: doctest-0.5.2
next goal: base (dependency of doctest-0.5.2)
rejecting: base-4.9.0.0/installed-4.9... (conflict: doctest => base>=4.0 &&
<4.5)
rejecting: 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)
Dependency tree exhaustively searched.