Manuel Chakravarty wrote:

> Care for legacy code is important, but H' will have to break 
> backwards compatibility in some places.  And especially where 
> you already rely on GHC extensions, you can't really expect 
> that H' will adopt features that have been available as GHC
> extensions in exactly the form that they were implemented in GHC.

Agreed. I was just motivating why we would want to upgrade code,
not arguing that we should be able to do that with no pain at all.

> We should be careful about where we break existing code, and 
> we should try to support automatic translation of H98 to H' code, 
> but any changes that we do not make now will become even more 
> difficult in the future when there is even more Haskell code.  
> Look at what is happening now already, industrial users applying 
> pressure on the committee to not change the language too much 
> for the sake of legacy code.  A clear indication that anything 
> we don't change now, we will have to live with forever.

I wasn't arguing for special treatment as an "industrial" user,
just listing one datapoint that I have to counter any impression
that the only or main cost to the community as a whole is fixing
what's on hackage.

> Hence, anything that is *important* to change, we should change now.


Agreed. It's just in this case the pain of changing will be huge and
the benefits marginal at best.

> We should mitigate the pain by having a H98 to H' translator

Such a translator would have to maintain existing layout etc, and
produce reasonably nice looking code in places where it makes changes.
Do we have any infrastructure that would make writing one easy?

Ganesh

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