--FIXME: see equivalentVersionRange for details
prop_simplifyVersionRange2'' :: VersionRange -> VersionRange -> Property
prop_simplifyVersionRange2'' r r' =
  r /= r' && r `equivalentVersionRange` r' ==>
       simplifyVersionRange r == simplifyVersionRange r'
    || isNoVersion r
    || isNoVersion r'
prop_simplifyVersionRange2'' :: VersionRange -> VersionRange -> Property
prop_simplifyVersionRange2'' r r' =
  r /= r' && r `equivalentVersionRange` r' ==>
       simplifyVersionRange r == simplifyVersionRange r'
    || isNoVersion r
    || isNoVersion r'
prop_simplifyVersionRange2'' r r' =
  r /= r' && r `equivalentVersionRange` r' ==>
       simplifyVersionRange r == simplifyVersionRange r'
    || isNoVersion r
    || isNoVersion r'