On Sun, Aug 11, 2013 at 10:00 PM, Richard Eisenberg
According to the Haskell 2010 report (http://www.haskell.org/onlinereport/haskell2010/haskellch11.html#x18-1820001...), a datatype with no constructors cannot derive any instances.
You're quite right! I should have looked over the ticket first, where Adam pointed this out.
But, instead of creating a new extension for this feature, what about just co-opting EmptyDataDecls? More concretely, I propose this:
Under H98: EmptyDataDecls allows both the declaration of empty data decls and deriving instances for them.
Under H2010: EmptyDataDecls allows deriving instances for empty data decls.
This proposal brings the annoyance that H2010 no longer implies EmptyDataDecls.
Thoughts?
Richard
IMHO, I'd find this inconsistency in extension behavior much more annoying than just going against the standard on this note. But that's just my 0.02c. -- Regards, Austin - PGP: 4096R/0x91384671