Add tests for Safe Haskell Typeable instances feature

1 files changed, 41 insertions, 0 deletions

diff --git a/testsuite/tests/safeHaskell/safeLanguage/SafeLang14.hs b/testsuite/tests/safeHaskell/safeLanguage/SafeLang14.hs
new file mode 100644
index 0000000000..9be68a3abb
--- /dev/null
+++ b/testsuite/tests/safeHaskell/safeLanguage/SafeLang14.hs
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+{-# LANGUAGE DeriveDataTypeable, StandaloneDeriving #-}
+-- | This shows how to use typeable to perform unsafe
+-- casts. Basically its an example of what Safe Haskell
+-- should disallow. SafeLang14 will do that.
+module Main where
+
+import SafeLang13_A
+import Data.Typeable
+
+data H = H String deriving (Typeable, Show)
+
+data G = G Int deriving (Show)
+
+instance Typeable G where
+    typeOf _ = typeOf (undefined :: H)
+
+instance Typeable P where
+    typeOf _ = typeOf (undefined :: G)
+
+{-
+deriving instance Typeable G
+
+deriving instance Typeable P
+-}
+
+main = do
+    let h = H "Hello World"
+        g = G 1
+--        Just h' = (cast h) :: Maybe G
+        Just p' = (cast p) :: Maybe G
+        Just px = (cast $ incrG p') :: Maybe P
+    putStrLn $ show h
+    putStrLn $ show g
+--    putStrLn $ show h'
+    putStrLn $ showP p
+    putStrLn $ show p'
+    putStrLn $ showP px
+
+incrG :: G -> G
+incrG (G n) = G $ n + 1
+