#14004: G -------------------------------------+------------------------------------- Reporter: zaoqi | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by AntC): Replying to [comment:12 zaoqi]:
Replying to [comment:11 AntC]:
So `instance Eq Dyn` will always return False.
How to write the correct `instance Eq Dyn`, do not change `data Dyn`.
The short answer is: `data Dyn` has the wrong definition for looking inside. Ben has given you one possibility in comment:8. A more simple one is: {{{ data Dyn a where Dyn :: Eq a => a -> Dyn a }}} If you can't change the definition of `Dyn` (why not?), you need to explain what you are trying to achieve. I suggest you ask a question on the cafe (or StackOverflow). GHC is behaving as intended. There's no fault, so Trac is not the place to look for that kind of help. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14004#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler