1 files changed, 38 insertions, 1 deletions
diff --git a/testsuite/tests/typecheck/should_fail/T22707.hs b/testsuite/tests/typecheck/should_fail/T22707.hs
index 35b0817ec2..38606d57c0 100644
--- a/testsuite/tests/typecheck/should_fail/T22707.hs
+++ b/testsuite/tests/typecheck/should_fail/T22707.hs
@@ -3,11 +3,48 @@ module T22707 where
 newtype Cont o i a = Cont {runCont ::(a -> i) -> o }
 
 t1:: Cont (i2 -> o) i1 a -> Cont o i2 (a -> i1)
-t1 c = Cont $ \ati1tti2 -> (runCont c) (ati1tti2 $ \a -> evalCont (t1 c) >>== \ati1 -> return ati1 a )
+t1 c = Cont $ \ati1tti2 -> (runCont c) (ati1tti2 $ \xa -> evalCont (t1 c) >>== \ati1 -> return ati1 xa )
+
+
+{-  This is a complicated and confused program.
+    We end up unifying
+        m0 p0 q0 b0 ~ (->) LiftedRep LiftedRep t1 t2
+    which unifies q0~LiftedRep, and m0 with the (polymorphically-kinded)
+      (->) LiftedRep
+    Getting a decent error message out of this mess is a challenge!
+
+  runCont :: Cont oo ii aa -> ((aa -> ii) -> oo)
+  (>>==)  :: forall k (m:k->k->*->*) (p:k) (q:k) a.
+             PMonad m => m p q a -> (a -> m q r b) -> m p r b
+
+  c :: Cont (i2 -> o) i1 a
+  Result type: Cont o i2 (a -> i1)
+  Arg of cont: ((a->i1) -> i2) -> o
+  ati1tti2 :: (a->i1) -> i2
+  runCont c :: (a -> i1) -> i2 -> o
+  xa :: a -> i1
+  t1 c :: Cont o i2 (a -> i1)
+  evalCont (t1 c) :: o
+  (>>==) @k0,m0,p0,q0,a0,r0) (evalCont (t1 c))
+     [W] o ~ m0 p0 q0 a0
+  ati1 :: a10
+  return @m10 @a10 ati1 xa :: a11
+    [W] m10 a10 ~ (a -> i1) -> a11
+    => [W] m10 ~ (->) @LiftedRep @LiftedRep (a -> i1) 
+       [W] a10 ~ a11
+  Result of (\ati1 -> ..)
+    (>>==) @m0,p0,q0,a0) (evalCont (t1 c)) (\ati1 -> ..) :: m0 p0 r0 b0
+    [W] a11 ~ m0 q0 r0 b0
+  Result of (>>==) call
+    [W] i1 ~ m0 p0 r0 b0
+-}
 
 evalCont:: Cont o a a -> o
 evalCont c = (runCont c)id
 
+instance Functor (Cont p p) where
+instance Applicative (Cont p p) where
+
 instance Monad (Cont p p) where
   return a = Cont ($ a)
   (>>=) = (>>==)