Resolving dependencies... Configuring ghc-paths-0.1.0.9... Configuring mtl-2.2.1... Building mtl-2.2.1... Building ghc-paths-0.1.0.9... Installed mtl-2.2.1 Configuring parallel-3.2.1.0... Configuring random-1.1... Installed ghc-paths-0.1.0.9 Building parallel-3.2.1.0... Building random-1.1... Configuring text-1.2.2.1... Installed parallel-3.2.1.0 Building text-1.2.2.1... Installed random-1.1 Installed text-1.2.2.1 Configuring zeno-0.2.0.1... Building zeno-0.2.0.1... Failed to install zeno-0.2.0.1 Build log ( /home/builder/.cabal/logs/zeno-0.2.0.1.log ): cabal: Entering directory '/tmp/cabal-tmp-28182/zeno-0.2.0.1' Configuring zeno-0.2.0.1... Building zeno-0.2.0.1... Preprocessing executable 'zeno' for zeno-0.2.0.1... src/Zeno/HaskellParser.hs:1:14: warning: -XDoRec is deprecated: use -XRecursiveDo or pragma {-# LANGUAGE RecursiveDo #-} instead [ 1 of 25] Compiling Zeno.Prelude ( src/Zeno/Prelude.hs, dist/build/zeno/zeno-tmp/Zeno/Prelude.o ) src/Zeno/Prelude.hs:131:10: error: Duplicate instance declarations: instance Functor First -- Defined at src/Zeno/Prelude.hs:131:10 instance Functor First -- Defined in ‘Data.Monoid’ cabal: Leaving directory '/tmp/cabal-tmp-28182/zeno-0.2.0.1' cabal: Error: some packages failed to install: zeno-0.2.0.1 failed during the building phase. The exception was: ExitFailure 1