-- Compute mutually recursive groups of tycons in topological order.
--
tyConGroups :: [TyCon] -> [TyConGroup]
tyConGroups tcs = map mk_grp (stronglyConnCompFromEdgedVertices edges)
  where
    edges = [((tc, ds), tc, uniqSetToList ds) | tc <- tcs
                                , let ds = tyConsOfTyCon tc]

    mk_grp (AcyclicSCC (tc, ds)) = ([tc], ds)
    mk_grp (CyclicSCC els)       = (tcs, unionManyUniqSets dss)
      where
        (tcs, dss) = unzip els

-- |Collect the set of TyCons used by the representation of some data type.
--
tyConGroups :: [TyCon] -> [TyConGroup]
tyConGroups tcs = map mk_grp (stronglyConnCompFromEdgedVertices edges)
  where
    edges = [((tc, ds), tc, uniqSetToList ds) | tc <- tcs
                                , let ds = tyConsOfTyCon tc]

    mk_grp (AcyclicSCC (tc, ds)) = ([tc], ds)
    mk_grp (CyclicSCC els)       = (tcs, unionManyUniqSets dss)
      where
        (tcs, dss) = unzip els

-- |Collect the set of TyCons used by the representation of some data type.
--
tyConGroups tcs = map mk_grp (stronglyConnCompFromEdgedVertices edges)
  where
    edges = [((tc, ds), tc, uniqSetToList ds) | tc <- tcs
                                , let ds = tyConsOfTyCon tc]

    mk_grp (AcyclicSCC (tc, ds)) = ([tc], ds)
    mk_grp (CyclicSCC els)       = (tcs, unionManyUniqSets dss)
      where
        (tcs, dss) = unzip els

-- |Collect the set of TyCons used by the representation of some data type.
--