Resolving dependencies...
Configuring mtl-2.2.1...
Building mtl-2.2.1...
Installed mtl-2.2.1
Configuring regex-base-0.93.2...
Building regex-base-0.93.2...
Installed regex-base-0.93.2
Configuring regex-posix-0.95.2...
Building regex-posix-0.95.2...
Installed regex-posix-0.95.2
Configuring regex-posix-unittest-1.0...
Building regex-posix-unittest-1.0...
Failed to install regex-posix-unittest-1.0
Build log ( /home/builder/.cabal/logs/regex-posix-unittest-1.0.log ):
cabal: Entering directory '/tmp/cabal-tmp-1196/regex-posix-unittest-1.0'
Configuring regex-posix-unittest-1.0...
Building regex-posix-unittest-1.0...
Preprocessing executable 'regex-posix-unittest' for
regex-posix-unittest-1.0...
[1 of 2] Compiling Paths_regex_posix_unittest ( dist/build/autogen/Paths_regex_posix_unittest.hs, dist/build/regex-posix-unittest/regex-posix-unittest-tmp/Paths_regex_posix_unittest.o )
[2 of 2] Compiling Main             ( Main.hs, dist/build/regex-posix-unittest/regex-posix-unittest-tmp/Main.o )

Main.hs:35:10: error:
    Duplicate instance declarations:
      instance IsString (Seq Char) -- Defined at Main.hs:35:10
      instance IsString (Seq Char) -- Defined in ‘Data.Sequence’
cabal: Leaving directory '/tmp/cabal-tmp-1196/regex-posix-unittest-1.0'
cabal: Error: some packages failed to install:
regex-posix-unittest-1.0 failed during the building phase. The exception was:
ExitFailure 1