# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
#
-u MatchGroup.foo
===
 module MatchGroup where
 
 foo :: [a] -> a
 foo [] = error "foo: empty list"
 foo (x:xs) = x
 
 main :: IO ()
 main = do
   -- unfold tests
-  print (foo [])
+  print (error "foo: empty list")
-  print $ foo (1:[2])
+  print $ 1