1 files changed, 56 insertions, 0 deletions
diff --git a/testsuite/tests/typecheck/should_fail/FrozenErrorTests.hs b/testsuite/tests/typecheck/should_fail/FrozenErrorTests.hs
new file mode 100644
index 0000000000..bea5495518
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/FrozenErrorTests.hs
@@ -0,0 +1,56 @@
+{-# LANGUAGE RankNTypes, GADTs, TypeFamilies #-}
+module Test where 
+
+
+data T a where 
+  MkT :: a -> T a 
+  MkT2 :: forall a b. (b ~ T b) => b -> T a
+  MkT3 :: forall a. (a ~ Bool) => T a 
+-- Occurs checks in givens
+foo :: forall a. (a ~ T a) => a -> a 
+foo x = x 
+
+blah x = case x of 
+           MkT2 y -> ()
+
+-- Mismatches in givens 
+bloh :: T Int -> () 
+bloh x = case x of 
+           MkT3 -> () 
+
+type family F a b 
+type family G a b
+type instance F a Bool = a 
+type instance G a Char = a
+
+goo1 :: forall a b. (F a b ~ [a]) => b -> a  -> a
+goo1 = undefined 
+
+goo2 :: forall a. G a Char ~ [Int] => a -> a
+goo2 = undefined
+
+-- Just an occurs check
+test1 = goo1 False undefined
+
+-- A frozen occurs check, now transformed to decomposition error
+test2 = goo2 (goo1 False undefined)
+test3 = goo1 False (goo2 undefined)
+
+
+-- A frozen occurs check, now transformed to both a decomposition and occurs check
+data M a where 
+  M :: M a 
+data T2 a b where
+  T2 :: T2 a b 
+
+goo3 :: forall a b. F a b ~ T2 (M a) a => b -> a -> a 
+goo3 = undefined
+
+goo4 :: forall a c. G a Char ~ T2 (T2 c c) c => a -> a
+goo4 = undefined 
+
+test4 = goo4 (goo3 False undefined)
+test5 = goo3 False (goo4 undefined)
+
+
+