On Thu, Mar 8, 2012 at 1:00 PM, Greg Weber
This discussion has largely centered around trying to come up with a hack that desugars to Haskell's existing language constructs.
There is an alternative to a desugaring hack: add a real record construct to the language.
I am not sure what distinction you are making between "real record construct" and "desugaring hack". As far as I can see, all major proposals currently desugar to type classes... not as a "hack" but because type classes *are* how Haskell does type-directed resolution. I don't think there are any ground rules set against proposing a system that doesn't use type classes. If you wanted, you could certainly propose a system that defines brand new and potentially very different semantics for a desired record system from scratch, and has nothing to do with type classes. I tend to think it would be a poor idea, both because it would be a large amount of work to be sure the semantics are even nailed down well, and because then the progress of abstraction over that new construct would happen independently from the existing progress of abstraction over type classes, and we'd end up with a more complex and warty language as a result. In any case, I'm in agreement that "stop arguing about semantics and just implement something" is a very bad idea. We aren't arguing about implementation choices here; we're arguing about pretty fundamental questions of semantics of records and labels, and the way to settle fundamental questions about the record system we hope to be using in 10 years time is not based on who has time after work for GHC hacking this month. -- Chris Smith