Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: sifflet (user goal)
rejecting: sifflet-2.2.1, 2.2.0, 2.1.0, 2.0.0.0, 1.2.5.1, 1.2.5, 1.2.4, 1.2.3,
1.2.2, 1.2.1, 1.2, 1.1, 1.0 (global constraint requires ==0.1.7)
trying: sifflet-0.1.7
trying: base-4.7.0.1/installed-e4b... (dependency of sifflet-0.1.7)
next goal: mtl (dependency of sifflet-0.1.7)
rejecting: mtl-2.2.1, 2.2.0.1, 2.2, 2.1.3.1, 2.1.2, 2.1.1, 2.1, 2.0.1.1,
2.0.1.0, 2.0.0.0 (conflict: sifflet => mtl>=1.1 && <2.0)
rejecting: mtl-1.1.1.1, 1.1.1.0 (conflict: base==4.7.0.1/installed-e4b..., mtl
=> base<4.6)
rejecting: mtl-1.1.0.2, 1.1.0.1, 1.1.0.0 (conflict:
base==4.7.0.1/installed-e4b..., mtl => base<4.3)
rejecting: mtl-1.0 (conflict: sifflet => mtl>=1.1 && <2.0)
Dependency tree exhaustively searched.