1 files changed, 18 insertions, 0 deletions
diff --git a/testsuite/tests/patsyn/should_compile/T17775-singleton.hs b/testsuite/tests/patsyn/should_compile/T17775-singleton.hs
new file mode 100644
index 0000000000..651dff583a
--- /dev/null
+++ b/testsuite/tests/patsyn/should_compile/T17775-singleton.hs
@@ -0,0 +1,18 @@
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE ViewPatterns #-}
+module Bug where
+
+-- Ryan Scott (on MR !2600) said this failed
+
+type T = forall a. a -> ()
+
+toT :: () -> T
+toT x _ = x
+
+pattern ToT :: T -> ()
+pattern ToT{x} <- (toT -> x)
+
+-- f (toT -> (x::T)) = True
+