5 files changed, 54 insertions, 2 deletions
diff --git a/testsuite/tests/backpack/should_compile/all.T b/testsuite/tests/backpack/should_compile/all.T
index 07c1ed27ec..9a2edebd8e 100644
--- a/testsuite/tests/backpack/should_compile/all.T
+++ b/testsuite/tests/backpack/should_compile/all.T
@@ -52,6 +52,7 @@ test('bkp57', normal, backpack_compile, [''])
 test('bkp58', normal, backpack_compile, [''])
 test('bkp59', normal, backpack_compile, [''])
 test('bkp60', normal, backpack_compile, [''])
+test('bkp61', normal, backpack_compile, [''])
 
 test('T13140', normal, backpack_compile, [''])
 test('T13149', expect_broken(13149), backpack_compile, [''])
diff --git a/testsuite/tests/backpack/should_compile/bkp09.bkp b/testsuite/tests/backpack/should_compile/bkp09.bkp
index 64cf447715..68b9677d56 100644
--- a/testsuite/tests/backpack/should_compile/bkp09.bkp
+++ b/testsuite/tests/backpack/should_compile/bkp09.bkp
@@ -7,7 +7,7 @@ unit p where
         data T a = MkT (S a)
         data S a = MkS a
 
--- keept his synced up!
+-- keep this synced up!
 unit q where
     signature H where
         data T a = MkT (S a)
diff --git a/testsuite/tests/backpack/should_compile/bkp15.bkp b/testsuite/tests/backpack/should_compile/bkp15.bkp
index c661eafe6f..48058417a9 100644
--- a/testsuite/tests/backpack/should_compile/bkp15.bkp
+++ b/testsuite/tests/backpack/should_compile/bkp15.bkp
@@ -22,7 +22,7 @@ unit p where
         -- type instance Elem Int = Bool
         -- pattern Blub n = ("foo", n)
 
--- keept his synced up!
+-- keep this synced up!
 unit q where
     signature H where
         x :: (forall a. a -> a) -> (Int, Bool)
diff --git a/testsuite/tests/backpack/should_compile/bkp61.bkp b/testsuite/tests/backpack/should_compile/bkp61.bkp
new file mode 100644
index 0000000000..3ad7d721bb
--- /dev/null
+++ b/testsuite/tests/backpack/should_compile/bkp61.bkp
@@ -0,0 +1,36 @@
+-- Check that we can implement abstract data using a data family.
+
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE TypeFamilies #-}
+
+unit p where
+  signature H where
+    import Data.Kind
+    type T :: Bool -> Type
+    data T b
+    turnOff :: T True  -> T False
+    turnOn  :: T False -> T True
+  module A where
+    import H
+    foo :: T True -> T True
+    foo = turnOn . turnOff
+
+unit q where
+  module H where
+    import Data.Kind
+    type D :: Bool -> Type
+    data family D a
+    data instance D True  = DT
+    data instance D False = DF
+    turnOff DT = DF
+    turnOn  DF = DT
+
+    type S = D
+    type T = S
+
+unit r where
+  dependency q
+  dependency p[H=q:H]
+  module N where
+    import A
+    bar = foo . foo
diff --git a/testsuite/tests/backpack/should_compile/bkp61.stderr b/testsuite/tests/backpack/should_compile/bkp61.stderr
new file mode 100644
index 0000000000..808295964d
--- /dev/null
+++ b/testsuite/tests/backpack/should_compile/bkp61.stderr
@@ -0,0 +1,15 @@
+[1 of 3] Processing p
+  [1 of 2] Compiling H[sig]           ( p\H.hsig, nothing )
+  [2 of 2] Compiling A                ( p\A.hs, nothing )
+[2 of 3] Processing q
+  Instantiating q
+  [1 of 1] Compiling H                ( q\H.hs, bkp61.out\q\H.o )
+[3 of 3] Processing r
+  Instantiating r
+  [1 of 2] Including q
+  [2 of 2] Including p[H=q:H]
+    Instantiating p[H=q:H]
+    [1 of 2] Compiling H[sig]           ( p\H.hsig, bkp61.out\p\p-D5Mg3foBSCrDbQDKH4WGSG\H.o )
+    [2 of 2] Compiling A                ( p\A.hs, bkp61.out\p\p-D5Mg3foBSCrDbQDKH4WGSG\A.o )
+  [1 of 2] Compiling N                ( r\N.hs, bkp61.out\r\N.o )
+  [2 of 2] Instantiating p