Technically, EmptyDataDecls is part of Haskell 2010, so it is standard these days (and H2010 is our default in GHC.)
As far as I know, the 2010 standard doesn't address this point about deriving for empty data decls, but I agree with your reasoning here. It's more consistent to have it apply to all of the base classes which are derivable. On Sun, Aug 11, 2013 at 9:14 PM, Richard Eisenberg <[email protected]> wrote: > Maybe it's best if Show, Ord, etc., echo the new behavior for Eq, if > EmmptyDataDecls is specified. The reason for the check in cond_stdOK is to > make sure that we're conforming to the Haskell standard. But, if the user has > specified EmptyDataDecls, then we're not bound to that requirement anymore. > So, to me, it seems reasonable that the "null data_cons" check should be > omitted for any class if EmptyDataDecls is specified. > > What do others think? This would go beyond the scope of the particular > reported bug, but it seems to make sense to me. > > Thanks, > Richard > > On Aug 9, 2013, at 3:16 PM, Ömer Sinan Ağacan wrote: > >> Removing `null data_cons`(compiler/typecheck/TcDeriv.lhs 1105) check >> for eq instance declarations fixes this, code generation part would be >> same(changes in TcGenDeriv.hs were wrong and TcGenDeriv needs to be >> unchanged)but I'm not sure how to remove that check only for eq >> instance(Show, Ord, etc. sould still fail with same error message and >> they're checked by same function, `cond_stdOK` -- line 1053). >> >> --- >> Ömer Sinan Ağacan >> http://osa1.net >> >> _______________________________________________ >> ghc-devs mailing list >> [email protected] >> http://www.haskell.org/mailman/listinfo/ghc-devs >> > > > _______________________________________________ > ghc-devs mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/ghc-devs -- Regards, Austin - PGP: 4096R/0x91384671 _______________________________________________ ghc-devs mailing list [email protected] http://www.haskell.org/mailman/listinfo/ghc-devs
