diff options
Diffstat (limited to 'testsuite/tests/typecheck/should_fail/T22648c.hs')
| -rw-r--r-- | testsuite/tests/typecheck/should_fail/T22648c.hs | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/testsuite/tests/typecheck/should_fail/T22648c.hs b/testsuite/tests/typecheck/should_fail/T22648c.hs new file mode 100644 index 0000000000..e81d97da0e --- /dev/null +++ b/testsuite/tests/typecheck/should_fail/T22648c.hs @@ -0,0 +1,24 @@ +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE UndecidableInstances #-} +{-# LANGUAGE DataKinds #-} + +module T22648c where + +import GHC.TypeLits (Nat) +import Data.Kind (Type) + +-- 1. the (i :: Nat) parameter to avoid conflicting instances +-- 2. the (Type ->) parameter is to prevent instantiation of invisible variables + +type family Infer (i :: Nat) :: Type -> forall {a}. a +type family Invis (i :: Nat) :: Type -> forall a. a +type family Vis (i :: Nat) :: Type -> forall a -> a + +type instance Vis 1 = Invis 0 -- Bad +type instance Invis 2 = Vis 0 -- Bad + +type instance Vis 3 = Infer 0 -- Bad +type instance Infer 4 = Vis 0 -- Bad + +type instance Invis 5 = Infer 0 -- Bad +type instance Infer 6 = Invis 0 -- Ok
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