3 files changed, 56 insertions, 0 deletions
diff --git a/testsuite/tests/stranal/sigs/T22241.hs b/testsuite/tests/stranal/sigs/T22241.hs
new file mode 100644
index 0000000000..21bf7b1d6b
--- /dev/null
+++ b/testsuite/tests/stranal/sigs/T22241.hs
@@ -0,0 +1,31 @@
+module T22241 where
+
+data D = D { unD :: !Int }
+
+-- We should unbox y here, which only happens if DmdAnal sees that $WD will
+-- unbox it.
+f :: Bool -> Int -> D
+f x y = D (go x)
+  where
+    go False = y
+    go True  = go False
+{-# NOINLINE f #-}
+
+
+
+data T a = T Int !a
+get (T _ x) = x
+
+-- Here, the goal is to discard `unD (f True z)` and thus `z` as absent by
+-- looking through $WT in `j` *during the first pass of DmdAnal*!
+g :: Bool -> Int -> Int -> Bool
+g x y z | even y    = get (fst t)
+        | y > 13    = not (get (fst t))
+        | otherwise = False
+  where
+    t | x         = j (unD (f True z))
+      | otherwise = j (unD (f False z))
+      where
+        j a = (T a x, True)
+        {-# NOINLINE j #-}
+{-# NOINLINE g #-}
diff --git a/testsuite/tests/stranal/sigs/T22241.stderr b/testsuite/tests/stranal/sigs/T22241.stderr
new file mode 100644
index 0000000000..284fe2cf76
--- /dev/null
+++ b/testsuite/tests/stranal/sigs/T22241.stderr
@@ -0,0 +1,24 @@
+
+==================== Strictness signatures ====================
+T22241.f: <1L><S!P(L)>
+T22241.g: <L><1!P(L)><A>
+T22241.get: <1!P(A,1L)>
+T22241.unD: <1!P(L)>
+
+
+
+==================== Cpr signatures ====================
+T22241.f: 1
+T22241.g:
+T22241.get:
+T22241.unD: 1
+
+
+
+==================== Strictness signatures ====================
+T22241.f: <1L><1!P(SL)>
+T22241.g: <ML><1!P(L)><A>
+T22241.get: <1!P(A,1L)>
+T22241.unD: <1!P(L)>
+
+
diff --git a/testsuite/tests/stranal/sigs/all.T b/testsuite/tests/stranal/sigs/all.T
index 73ecf7be57..01ea48cfe8 100644
--- a/testsuite/tests/stranal/sigs/all.T
+++ b/testsuite/tests/stranal/sigs/all.T
@@ -37,3 +37,4 @@ test('T21717', normal, compile, [''])
 test('T21754', normal, compile, [''])
 test('T21888', normal, compile, [''])
 test('T21888a', normal, compile, [''])
+test('T22241', normal, compile, [''])