Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: sifflet (user goal)
rejecting: sifflet-2.3.0, sifflet-2.2.1, sifflet-2.2.0, sifflet-2.1.0,
sifflet-2.0.0.0, sifflet-1.2.5.1, sifflet-1.2.5, sifflet-1.2.4, sifflet-1.2.3,
sifflet-1.2.2 (constraint from user target requires ==1.2.1)
trying: sifflet-1.2.1
next goal: base (dependency of sifflet-1.2.1)
rejecting: base-4.9.0.0/installed-4.9... (conflict: sifflet => base>=4.0 &&
<4.3)
rejecting: base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0,
base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0,
base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0,
base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0,
base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable
package requires installed instance)
Dependency tree exhaustively searched.