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, sifflet-1.2.1, sifflet-1.2, sifflet-1.1, sifflet-1.0
(constraint from user target requires ==0.1.7)
trying: sifflet-0.1.7
trying: base-4.9.0.0/installed-4.9... (dependency of sifflet-0.1.7)
next goal: mtl (dependency of sifflet-0.1.7)
rejecting: mtl-2.2.1, mtl-2.2.0.1, mtl-2.2, mtl-2.1.3.1, mtl-2.1.2, mtl-2.1.1,
mtl-2.1, mtl-2.0.1.1, mtl-2.0.1.0, mtl-2.0.0.0 (conflict: sifflet => mtl>=1.1
&& <2.0)
rejecting: mtl-1.1.1.1, mtl-1.1.1.0 (conflict: base==4.9.0.0/installed-4.9...,
mtl => base<4.6)
rejecting: mtl-1.1.0.2, mtl-1.1.0.1, mtl-1.1.0.0 (conflict:
base==4.9.0.0/installed-4.9..., mtl => base<4.3)
rejecting: mtl-1.0 (conflict: sifflet => mtl>=1.1 && <2.0)
Dependency tree exhaustively searched.