Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: RBTree (user goal)
rejecting: RBTree-0.0.5, 0.0.4, 0.0.3 (global constraint requires ==0.0.2)
trying: RBTree-0.0.2
next goal: base (dependency of RBTree-0.0.2)
rejecting: base-4.8.1.0/installed-4f7... (conflict: RBTree => base==4)
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.