Resolving dependencies...
cabal: Could not resolve dependencies:
trying: gtk2hs-hello-1.1.0.0 (user goal)
trying: mtl-2.2.1 (dependency of gtk3-0.13.9)
next goal: transformers (dependency of gtk2hs-hello-1.1.0.0)
rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.2.0,
transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0,
transformers-0.4.3.0, transformers-0.4.2.0, transformers-0.4.1.0 (conflict:
gtk2hs-hello => transformers>=0.3.0.0 && <0.4)
rejecting: transformers-0.3.0.0 (conflict: mtl => transformers>=0.4 && <0.6)
rejecting: transformers-0.2.2.1, transformers-0.2.1.0, transformers-0.2.0.0,
transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0,
transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0,
transformers-0.5.0.2, transformers-0.4.0.0, transformers-0.2.2.0,
transformers-0.1.0.0 (conflict: gtk2hs-hello => transformers>=0.3.0.0 && <0.4)
Dependency tree exhaustively searched.