Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: pqueue-mtl (user goal)
rejecting: pqueue-mtl-1.0.7, 1.0.6, 1.0.5 (global constraint requires ==1.0.4)
trying: pqueue-mtl-1.0.4
trying: base-4.8.1.0/installed-4f7... (dependency of pqueue-mtl-1.0.4)
next goal: MaybeT (dependency of pqueue-mtl-1.0.4)
rejecting: MaybeT-0.1.2, 0.1.1 (conflict: base==4.8.1.0/installed-4f7...,
MaybeT => base<4.8)
rejecting: MaybeT-0.1.0 (conflict: base==4.8.1.0/installed-4f7..., MaybeT =>
base<4.3)
Dependency tree exhaustively searched.