diff options
Diffstat (limited to 'testsuite/tests/gadt/gadt21.hs')
-rw-r--r-- | testsuite/tests/gadt/gadt21.hs | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/testsuite/tests/gadt/gadt21.hs b/testsuite/tests/gadt/gadt21.hs new file mode 100644 index 0000000000..b452d083c1 --- /dev/null +++ b/testsuite/tests/gadt/gadt21.hs @@ -0,0 +1,23 @@ +{-# LANGUAGE GADTs, ExistentialQuantification, KindSignatures, Rank2Types #-} + +-- Fails (needs the (Ord a) in TypeSet +-- c.f. gadt22.hs + +module Expr where + +import Data.Set (Set) + +data Type a where + TypeInt :: Type Int + TypeSet :: {- Ord a => -} Type a -> Type (Set a) + TypeFun :: Type a -> Type b -> Type (a -> b) + +data Expr :: * -> * where + Const :: Type a -> a -> Expr a + +data DynExpr = forall a. DynExpr (Expr a) + +withOrdDynExpr :: DynExpr -> (forall a. Ord a => Expr a -> b) -> Maybe b +withOrdDynExpr (DynExpr e@(Const (TypeSet _) _)) f = Just (f e) +withOrdDynExpr (DynExpr e@(Const TypeInt _)) f = Just (f e) +withOrdDynExpr _ _ = Nothing |