1 files changed, 15 insertions, 0 deletions
diff --git a/testsuite/tests/typecheck/should_fail/T21158.hs b/testsuite/tests/typecheck/should_fail/T21158.hs
new file mode 100644
index 0000000000..282989f5b8
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T21158.hs
@@ -0,0 +1,15 @@
+{-# LANGUAGE TypeFamilies #-}
+module T21158 where
+
+type family F a
+
+data T b = MkT { x :: [Int], y :: [F b] }
+
+emptyT :: T b
+emptyT = MkT [] []
+
+foo1 :: [Int] -> T b
+foo1  newx = emptyT { x = newx }
+
+foo2 :: [Int] -> T b
+foo2  newx = case emptyT of MkT x y -> MkT newx y