Bug#867873: haskell-vector FTBFS: error: Duplicate instance declarations

[Adrian Bunk]

Source: haskell-vector
Version: 0.11.0.0-7
Severity: serious

I can reproduce this on amd64:

https://buildd.debian.org/status/fetch.php?pkg=haskell-vector&arch=armhf&ver=0.11.0.0-7%2Bb1&stamp=1499645095&raw=0

...
[1 of 6] Compiling Utilities        ( tests/Utilities.hs, dist-ghc/build/vector-tests-O0/vector-tests-O0-tmp/Utilities.o )

tests/Utilities.hs:54:10: error:
    Duplicate instance declarations:
      instance Arbitrary a => Arbitrary (Identity a)
        -- Defined at tests/Utilities.hs:54:10
      instance [safe] Arbitrary a => Arbitrary (Identity a)
        -- Defined in `Test.QuickCheck.Arbitrary'

tests/Utilities.hs:57:10: error:
    Duplicate instance declarations:
      instance CoArbitrary a => CoArbitrary (Identity a)
        -- Defined at tests/Utilities.hs:57:10
      instance [safe] CoArbitrary a => CoArbitrary (Identity a)
        -- Defined in `Test.QuickCheck.Arbitrary'
/usr/share/cdbs/1/class/hlibrary.mk:147: recipe for target 'build-ghc-stamp' failed
make: *** [build-ghc-stamp] Error 1