imports :: Module -> M.Map ModulePath (S.Set (Identifier, Identifier))
imports (Module decls _) =
    M.fromListWith S.union [(p, [(i, s)]) | Import p i s _ <- DS.toList decls]
imports :: Module -> M.Map ModulePath (S.Set (Identifier, Identifier))
imports (Module decls _) =
    M.fromListWith S.union [(p, [(i, s)]) | Import p i s _ <- DS.toList decls]
imports (Module decls _) =
    M.fromListWith S.union [(p, [(i, s)]) | Import p i s _ <- DS.toList decls]