request for reviews for my first patch -- ticket 7401

9 Aug 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