Add test case for "spurious superclass constraints bug"

1 files changed, 30 insertions, 0 deletions

diff --git a/html-test/tests/SpuriousSuperclassConstraints.hs b/html-test/tests/SpuriousSuperclassConstraints.hs
new file mode 100644
index 00000000..d9e43e1c
--- /dev/null
+++ b/html-test/tests/SpuriousSuperclassConstraints.hs
@@ -0,0 +1,30 @@
+{-# LANGUAGE EmptyDataDecls, KindSignatures #-}
+-- |
+-- What is tested here:
+--
+-- Due to a change in GHC 7.6.1 we had a bug that superclass contraints were
+-- included in the instances list.  Edward K. repported it here:
+--
+--   <http://www.haskell.org/pipermail/haskell-cafe/2012-September/103600.html>
+--
+-- And here is the corresponding theard on glasgow-haskell-users:
+--
+--   <http://www.haskell.org/pipermail/glasgow-haskell-users/2012-September/022914.html>
+--
+-- It has been fixed in:
+--
+-- > 6ccf78e15a525282fef61bc4f58a279aa9c21771
+-- > Fix spurious superclass constraints bug.
+--
+module SpuriousSuperclassConstraints where
+
+import Control.Applicative
+
+data SomeType (f :: * -> *) a
+
+instance Functor (SomeType f) where
+  fmap = undefined
+
+instance Applicative f => Applicative (SomeType f) where
+  pure   = undefined
+  (<*>)  = undefined