Hi Adam,
very nice idea. As the others, I'm curious why you chose to implement SORF
in favor of the other ideas?
I just read the SORF proposal, and I'm a bit concerned about what error
messages would GHC issue when someone would type incorrect code involving
such records. Currently Haskell's error messages already pose a barrier for
newcomers (like "No instance for (Num (a -> a))"), and if records are
converted into those very complicated `Has` instances, type errors would be
probably undecipherable even for moderate skilled Haskell users.
Considering that records are a basic feature of Haskell and something that
people with OOP background are familiar with, this could result in a
feature that would without doubts deter many (if not most) newcomers. So do
you think it would be possible to implement it in such a way that users get
sensible type error messages?
Best regards,
Petr
2013/4/26 Adam Gundry
Hi,
I am hoping to do a GSoC project this year working on GHC, and have been pointed in the direction of the records issue (in particular, the desire to overload field names). This has been discussed on-and-off for years, and while there are lots of ideas [1], little has been implemented in GHC itself.
The plan would be to implement a solution to the "narrow issue" of overloaded field names, along the lines of Simon PJ's SORF proposal (on the wiki). This would provide a basis for experimentation with first-class record types. While there are still design issues to resolve, the broad plan is clear and I'm confident it can be implemented in a summer and without overly restricting future record system designs.
Does this sound like a reasonable strategy? I'd appreciate comments and criticism, although arguing about the details of the design should perhaps wait.
(A little about me: I'm a PhD student working on type inference for Haskell and dependent types, with about four years' Haskell experience including work on big type-system related projects. I am familiar with the theory behind GHC, but I haven't worked on the code before.)
Thanks,
Adam Gundry
[1] http://hackage.haskell.org/trac/ghc/wiki/Records
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