1 files changed, 13 insertions, 0 deletions
diff --git a/testsuite/tests/patsyn/should_fail/T21479.hs b/testsuite/tests/patsyn/should_fail/T21479.hs
new file mode 100644
index 0000000000..889e811e88
--- /dev/null
+++ b/testsuite/tests/patsyn/should_fail/T21479.hs
@@ -0,0 +1,13 @@
+{-# Language PatternSynonyms #-}
+{-# Language ViewPatterns #-}
+{-# Language GADTs #-}
+
+module T21479 where
+
+data T a where
+  MkT :: T Int
+
+foo :: () -> T a
+foo = foo
+
+pattern T1 <- (foo -> MkT)
+\ No newline at end of file