merge c@(Fixed (I v _) g1)   (Constrained rs) = go rs -- I tried "reverse rs" here, but it seems to slow things down ...
  where
    go []              = Right c
    go (d@(vr, g2) : vrs)
      | checkVR vr v   = go vrs
      | otherwise      = Left (CS.union (varToConflictSet g1) (varToConflictSet g2), (c, Constrained [d]))
merge c@(Fixed (I v _) g1)   (Constrained rs) = go rs -- I tried "reverse rs" here, but it seems to slow things down ...
  where
    go []              = Right c
    go (d@(vr, g2) : vrs)
      | checkVR vr v   = go vrs
      | otherwise      = Left (CS.union (varToConflictSet g1) (varToConflictSet g2), (c, Constrained [d]))
merge c@(Fixed (I v _) g1)   (Constrained rs) = go rs -- I tried "reverse rs" here, but it seems to slow things down ...
  where
    go []              = Right c
    go (d@(vr, g2) : vrs)
      | checkVR vr v   = go vrs
      | otherwise      = Left (CS.union (varToConflictSet g1) (varToConflictSet g2), (c, Constrained [d]))