Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: pqueue-mtl (user goal)
rejecting: pqueue-mtl-1.0.7, pqueue-mtl-1.0.6, pqueue-mtl-1.0.5 (constraint
from user target requires ==1.0.4)
trying: pqueue-mtl-1.0.4
trying: base-4.9.0.0/installed-4.9... (dependency of pqueue-mtl-1.0.4)
next goal: MaybeT (dependency of pqueue-mtl-1.0.4)
rejecting: MaybeT-0.1.2, MaybeT-0.1.1 (conflict:
base==4.9.0.0/installed-4.9..., MaybeT => base<4.8)
rejecting: MaybeT-0.1.0 (conflict: base==4.9.0.0/installed-4.9..., MaybeT =>
base<4.3)
Dependency tree exhaustively searched.