1 files changed, 37 insertions, 0 deletions
diff --git a/testsuite/tests/stranal/should_compile/T21150.hs b/testsuite/tests/stranal/should_compile/T21150.hs
new file mode 100644
index 0000000000..520b7d9d77
--- /dev/null
+++ b/testsuite/tests/stranal/should_compile/T21150.hs
@@ -0,0 +1,37 @@
+-- | The idea here is that t* should never be inlined into g*.
+-- That may happen if the absent arguments of g* are dropped without care,
+-- making $wg* appear as if all its lambdas are oneShot afterwards.
+--
+-- So in these cases, we replace absent args with `Void#` instead in order
+-- to preserve lambda groups.
+module T21150 where
+
+import GHC.Exts
+
+f :: Int -> Int -> Int -> Maybe Int
+f x y z = (+) <$> g x y z <*> g x z y
+  where
+    t :: Int
+    t = sum [0..x]
+    g :: Int -> Int -> Int -> Maybe Int
+    g _ = oneShot $ \_ -> oneShot $ \z -> Just (y + z + t)
+    {-# NOINLINE g #-}
+
+f2 :: Int -> Int -> Int -> Maybe Int
+f2 x y z = (+) <$> g' y <*> g' z
+  where
+    t2 :: Int
+    t2 = sum [0..x]
+    g' = g2 x
+    g2 :: Int -> Int -> Maybe Int
+    g2 = oneShot $ \y _ -> Just (y + z + t2)
+    {-# NOINLINE g2 #-}
+
+f3 :: Int -> Int -> Int -> Maybe Int
+f3 x y z = (+) <$> g3 x y z <*> g3 x z y
+  where
+    t3 :: Int
+    t3 = sum [0..x]
+    g3 :: Int -> Int -> Int -> Maybe Int
+    g3 = oneShot $ \y z _ -> Just (y + z + t3)
+    {-# NOINLINE g3 #-}