diff options
Diffstat (limited to 'testsuite/tests/indexed-types/should_compile/T4160.hs')
| -rw-r--r-- | testsuite/tests/indexed-types/should_compile/T4160.hs | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/testsuite/tests/indexed-types/should_compile/T4160.hs b/testsuite/tests/indexed-types/should_compile/T4160.hs new file mode 100644 index 0000000000..f13aafa103 --- /dev/null +++ b/testsuite/tests/indexed-types/should_compile/T4160.hs @@ -0,0 +1,18 @@ +{-# LANGUAGE FlexibleContexts, MultiParamTypeClasses, TypeFamilies #-} +module Foo where + +data P f g r = f r :*: g r +type family TrieMapT (f :: * -> *) :: * -> (* -> *) -> * -> * +newtype PMap m1 (m2 :: * -> (* -> *) -> * -> *) k (a :: * -> *) ix = PMap (m1 k (m2 k a) ix) +type instance TrieMapT (P f g) = PMap (TrieMapT f) (TrieMapT g) + +class TrieKeyT f m where + unionT :: (TrieMapT f ~ m) => (f k -> a ix -> a ix -> a ix) -> + m k a ix -> m k a ix -> m k a ix + sizeT :: (TrieMapT f ~ m) => m k a ix -> Int + +instance (TrieKeyT f m1, TrieKeyT g m2) => TrieKeyT (P f g) (PMap m1 m2) where + unionT f (PMap m1) (PMap m2) = PMap (uT (\ a -> unionT (\ b -> f (a :*: b))) m1 m2) + where uT = unionT + sizeT = error "urk" + |