quchen authored Oct 08, 2016 and Herbert Valerio Riedel committed Oct 08, 2016

This definition was both in the module, and in a CPP-conditionally imported
other module. This patch removes this redundancy.

In the normal Cabal build this was not an issue, since it uses a newer version
of QuickCheck. The Stack-based build however still uses an old one, which lead
to both the import as well as the local definition from being in the code. The
testsuite would then fail with a duplicate definition error.

Fixes haskell/cabal#3950