Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: happy (user goal)
rejecting: happy-1.19.5, 1.19.4, 1.19.3, 1.19.2, 1.19.1, 1.19.0 (global
constraint requires ==1.18.11)
trying: happy-1.18.11
next goal: base (dependency of happy-1.18.11)
rejecting: base-4.8.1.0/installed-4f7... (conflict: happy => base>=4.5 &&
<4.7)
rejecting: base-4.8.1.0, 4.8.0.0, 4.7.0.2, 4.7.0.1, 4.7.0.0, 4.6.0.1, 4.6.0.0,
4.5.1.0, 4.5.0.0, 4.4.1.0, 4.4.0.0, 4.3.1.0, 4.3.0.0, 4.2.0.2, 4.2.0.1,
4.2.0.0, 4.1.0.0, 4.0.0.0, 3.0.3.2, 3.0.3.1 (global constraint requires
installed instance)
Dependency tree exhaustively searched.