Test Trac #7019

5 files changed, 46 insertions, 0 deletions

diff --git a/testsuite/tests/typecheck/should_fail/T7019.hs b/testsuite/tests/typecheck/should_fail/T7019.hs
new file mode 100644
index 0000000000..45df18ef92
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T7019.hs
@@ -0,0 +1,18 @@
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE Rank2Types           #-}
+{-# LANGUAGE ConstraintKinds      #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+module T7019a where
+
+newtype Free c a = Free { runFree :: forall r. c r => (a -> r) -> r }
+
+type C c = forall a. c (Free c a)
+
+-- Notice that C is a synonym, illegal!
+instance C c => Monad (Free c) where
+  return a = Free ($ a)
+  Free f >>= g = f g
+
+
diff --git a/testsuite/tests/typecheck/should_fail/T7019.stderr b/testsuite/tests/typecheck/should_fail/T7019.stderr
new file mode 100644
index 0000000000..43f1fe5209
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T7019.stderr
@@ -0,0 +1,6 @@
+
+T7019.hs:14:10:
+    Malformed predicate `C c'
+    In the context: (C c)
+    While checking an instance declaration
+    In the instance declaration for `Monad (Free c)'
diff --git a/testsuite/tests/typecheck/should_fail/T7019a.hs b/testsuite/tests/typecheck/should_fail/T7019a.hs
new file mode 100644
index 0000000000..a4fb4df252
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T7019a.hs
@@ -0,0 +1,14 @@
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE Rank2Types           #-}
+
+module T7019a where
+
+class Context c where
+  func1 :: c -> String
+
+-- Illegal forall in context
+class (forall b. Context (Associated a b)) => Class a where
+  data Associated a :: * -> *
+
+
diff --git a/testsuite/tests/typecheck/should_fail/T7019a.stderr b/testsuite/tests/typecheck/should_fail/T7019a.stderr
new file mode 100644
index 0000000000..2859f716b6
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T7019a.stderr
@@ -0,0 +1,6 @@
+
+T7019a.hs:11:1:
+    Malformed predicate `forall b. Context (Associated a b)'
+    In the context: (forall b. Context (Associated a b))
+    While checking the super-classes of class `Class'
+    In the class declaration for `Class'
diff --git a/testsuite/tests/typecheck/should_fail/all.T b/testsuite/tests/typecheck/should_fail/all.T
index 0d047bf1ad..9d4367b126 100644
--- a/testsuite/tests/typecheck/should_fail/all.T
+++ b/testsuite/tests/typecheck/should_fail/all.T
@@ -276,3 +276,5 @@ test('T5853', normal, compile_fail, [''])
 test('T6078', normal, compile_fail, [''])
 
 test('FDsFromGivens', normal, compile_fail, [''])
+test('T7019', normal, compile_fail,[''])
+test('T7019a', normal, compile_fail,[''])