{-# LANGUAGE RoleAnnotations #-}
{-# LANGUAGE ScopedTypeVariables #-}
unit prelude-sig where
    signature Prel where
        data List a = Nil | Cons a (List a)

unit arrays-sig where
    dependency prelude-sig[Prel=<Prel>]
    signature Array where
        import Prel
        data Arr i e
        something :: List (Arr i e)

unit structures where
    dependency arrays-sig[Prel=<Prel>, Array=<Array>]
    module Set where
        import Prel
        data S a = S (List a)
    module Graph where
        import Prel
        import Array
        data G = G (Arr Int [Int])
    module Tree where
        import Prel
        import Graph
        data T = T G

unit arrays-a where
    dependency prelude-sig[Prel=<Prel>]
    module Array where
        import qualified Prel as P
        type role Arr representational representational
        data Arr i e = MkArr ()
        something :: P.List (Arr i e)
        something = P.Nil

unit arrays-b where
    dependency prelude-sig[Prel=<Prel>]
    module Array where
        import Prel
        data Arr i e = ANil | ACons i e (Arr i e)
        -- NB: If you uncomment this, GHC decides to order the
        -- quantifiers the other way, and you are a sad panda.
        something :: Prel.List (Arr i e)
        something = Cons ANil Nil

unit graph-a where
    dependency arrays-a[Prel=<Prel>]
    dependency structures[Prel=<Prel>,Array=arrays-a[Prel=<Prel>]:Array] (Graph)

unit graph-b where
    dependency arrays-b[Prel=<Prel>]
    dependency structures[Prel=<Prel>,Array=arrays-b[Prel=<Prel>]:Array] (Graph)

unit multiinst where
    dependency arrays-a[Prel=<Prel>] (Array as AA)
    dependency arrays-b[Prel=<Prel>] (Array as AB)
    dependency structures[Prel=<Prel>,Array=arrays-a[Prel=<Prel>]:Array] (Graph as GA)
    dependency structures[Prel=<Prel>,Array=arrays-b[Prel=<Prel>]:Array] (Graph as GB)
    module Client where
        import qualified GA
        import qualified GB
        x = GA.G
        y = GB.G
        instance Show GA.G where
            show = undefined
        instance Show GB.G where
            show = undefined

unit applic-left where
    dependency arrays-a[Prel=<Prel>]
    dependency structures[Prel=<Prel>,Array=arrays-a[Prel=<Prel>]:Array] (Graph)
    module Left where
        import Graph
        x :: G
        x = undefined

unit applic-right where
    dependency arrays-a[Prel=<Prel>]
    dependency structures[Prel=<Prel>,Array=arrays-a[Prel=<Prel>]:Array] (Graph)
    module Right where
        import Graph
        f :: G -> G
        f = id

unit applic-bot where
    dependency applic-left[Prel=<Prel>]
    dependency applic-right[Prel=<Prel>]
    module Bot where
        import Left
        import Right
        g = f x