1 files changed, 41 insertions, 0 deletions
diff --git a/testsuite/tests/indexed-types/should_compile/Records.hs b/testsuite/tests/indexed-types/should_compile/Records.hs
new file mode 100644
index 0000000000..4a08125e30
--- /dev/null
+++ b/testsuite/tests/indexed-types/should_compile/Records.hs
@@ -0,0 +1,41 @@
+{-# LANGUAGE TypeFamilies #-}
+
+-- See Trac #1204
+
+module ShouldCompile where
+
+data FooC = FooC
+
+data family T c
+data instance T FooC = MkT { moo :: Int }
+
+t1 :: Int -> T FooC
+t1 i = MkT { moo = i }
+
+t2 :: T FooC -> Int
+t2 (MkT { moo = i }) = i
+
+t3 :: T FooC -> Int
+t3 m = moo m
+
+f :: T FooC -> T FooC
+f r = r { moo = 3 }
+
+
+------------------------------------------------------------------------------
+class D c where
+  data D1 c
+  works :: Int -> D1 c -> D1 c
+  buggy :: Int -> D1 c -> D1 c 
+  buggy2 :: Int -> D1 c -> D1 c
+
+instance D FooC where
+  data D1 FooC = D1F { noo :: Int }
+
+  works x d = d  -- d unchanged, so OK
+
+  buggy x d@(D1F { noo = k }) = 
+    d { noo = k + x }
+
+  buggy2 x d@(D1F { noo = k }) =
+    (d :: D1 FooC) { noo = k + x }