Hello Omer, It is almost certainly the case that the implementation of these functions should not be the constant return True function. Furthermore, the implementation should probably be done using: http://ghc.haskell.org/trac/ghc/ticket/2431 Edward Excerpts from Ömer Sinan Ağacan's message of Fri Aug 09 08:06:19 -0700 2013:
Hi all,
I just started GHC development made a commit for ticket 7401: http://ghc.haskell.org/trac/ghc/ticket/7401
My patch is here: https://github.com/osa1/ghc/commit/3ec257ff48372de30df59cd8854ce28954c9db95
`make test` succeeds. My test case for this patch is something like this:
data D deriving Eq
main :: IO () main = print ((undefined :: D) == (undefined :: D))
example:
➜ haskell ./ghc/inplace/bin/ghc-stage2 --interactive derive.hs GHCi, version 7.7.20130806: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( derive.hs, interpreted ) Ok, modules loaded: Main. ghci> main True it :: ()
This behavior(returning True) is consistent with standalone deriving version:
➜ haskell cat derive_standalone.hs {-# LANGUAGE StandaloneDeriving #-}
data D
deriving instance Eq D
main :: IO () main = print ((undefined :: D) == (undefined :: D))
➜ haskell ./ghc/inplace/bin/ghc-stage2 --interactive derive_standalone.hs GHCi, version 7.7.20130806: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( derive_standalone.hs, interpreted ) Ok, modules loaded: Main. ghci> main True it :: () ghci> Leaving GHCi.
However, if you want (==) implementation in this case to be `error "Void (==)`, I think I can also do that by first fixing the code generated by StandaloneDeriving extension and then fixing my current patch.
Any comments and reviews would be appreciated!
--- Ömer Sinan Ağacan http://osa1.net