1 files changed, 38 insertions, 0 deletions
diff --git a/testsuite/tests/deSugar/should_compile/T3263-2.hs b/testsuite/tests/deSugar/should_compile/T3263-2.hs
new file mode 100644
index 0000000000..71288062c5
--- /dev/null
+++ b/testsuite/tests/deSugar/should_compile/T3263-2.hs
@@ -0,0 +1,38 @@
+-- Trac #3263.  New kind of warning on monadic bindings that discard a monadic result
+
+module T3263 where
+
+import Control.Monad.Fix
+
+-- No warning
+t1 :: Monad m => m Int
+t1 = do
+  return 10
+
+-- No warning
+t2 :: Monad m => m (m Int)
+t2 = return (return 10)
+
+-- No warning
+t3 :: Monad m => m (m Int)
+t3 = do
+  return 10
+  return (return 10)
+
+-- Warning
+t4 :: forall m. Monad m => m Int
+t4 = do
+  return (return 10 :: m Int)
+  return 10
+
+-- No warning
+t5 :: forall m. Monad m => m Int
+t5 = do
+  _ <- return (return 10 :: m Int)
+  return 10
+
+-- Warning
+t6 :: forall m. MonadFix m => m Int
+t6 = mdo
+  return (return 10 :: m Int)
+  return 10
+\ No newline at end of file