1 files changed, 25 insertions, 0 deletions
diff --git a/testsuite/tests/typecheck/should_run/tcrun009.hs b/testsuite/tests/typecheck/should_run/tcrun009.hs
new file mode 100644
index 0000000000..1adc350084
--- /dev/null
+++ b/testsuite/tests/typecheck/should_run/tcrun009.hs
@@ -0,0 +1,25 @@
+{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-}
+
+-- !!! Functional dependencies
+
+module Main where
+
+class Foo a b | a -> b where
+    foo :: a -> b
+
+instance Foo [a] (Maybe a) where
+    foo []    = Nothing
+    foo (x:_) = Just x
+
+instance Foo (Maybe a) [a] where
+    foo Nothing  = []
+    foo (Just x) = [x]
+
+test3:: [a] -> [a]
+test3 = foo . foo
+-- First foo must use the first instance,
+-- second must use the second.  So we should
+-- get in effect: 	test3 (x:xs) = [x]
+
+main:: IO ()
+main = print (test3 "foo")