On Fri, Jan 15, 2016 at 3:03 PM, Jan Bracker
You just have to download the three files and run "cabal install" to reproduce the error.
It's never that easy, is it? Can you try in a cabal sandbox, with ghc-7.10.3. I'm getting: cabal: Could not resolve dependencies: trying: core-error-0.1 (user goal) next goal: base (dependency of core-error-0.1) rejecting: base-4.8.2.0/installed-0d6... (conflict: core-error => base==4.8.1.0) rejecting: 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 main config /home/thomas/.cabal/config requires installed instance) Dependency tree exhaustively searched. After relaxing the depenency on base (or is the problem only reproducible with base 4.8.1.0 that, in case we are done here), I get: Preprocessing library effect-monad-0.6.1... src/Control/Effect/State.hs:4:14: Warning: -XOverlappingInstances is deprecated: instead use per-instance pragmas OVERLAPPING/OVERLAPPABLE/OVERLAPS [ 1 of 17] Compiling Control.Effect.Helpers.List ( src/Control/Effect/Helpers/List.hs, dist/build/Control/Effect/Helpers/List.o ) [ 2 of 17] Compiling Control.Effect.Cond ( src/Control/Effect/Cond.hs, dist/build/Control/Effect/Cond.o ) [ 3 of 17] Compiling Control.Effect ( src/Control/Effect.hs, dist/build/Control/Effect.o ) [ 4 of 17] Compiling Control.Effect.Counter ( src/Control/Effect/Counter.hs, dist/build/Control/Effect/Counter.o ) [ 5 of 17] Compiling Control.Effect.CounterNat ( src/Control/Effect/CounterNat.hs, dist/build/Control/Effect/CounterNat.o ) [ 6 of 17] Compiling Control.Effect.Maybe ( src/Control/Effect/Maybe.hs, dist/build/Control/Effect/Maybe.o ) [ 7 of 17] Compiling Control.Effect.Monad ( src/Control/Effect/Monad.hs, dist/build/Control/Effect/Monad.o ) [ 8 of 17] Compiling Control.Effect.Parameterised ( src/Control/Effect/Parameterised.hs, dist/build/Control/Effect/Parameterised.o ) [ 9 of 17] Compiling Control.Effect.Reader ( src/Control/Effect/Reader.hs, dist/build/Control/Effect/Reader.o ) src/Control/Effect/Reader.hs:33:8: Not in scope: type constructor or class ‘Var’ src/Control/Effect/Reader.hs:33:28: Not in scope: type constructor or class ‘:->’ src/Control/Effect/Reader.hs:34:5: Not in scope: data constructor ‘Var’ src/Control/Effect/Reader.hs:34:24: Not in scope: data constructor ‘Var’ src/Control/Effect/Reader.hs:34:28: Not in scope: data constructor ‘:->’ Failed to install effect-monad-0.6.1