Enabling TypeHoles by default

Richard Eisenberg eir at cis.upenn.edu
Tue Jan 14 16:40:27 UTC 2014

Perhaps I'm being silly, but if the extended errors are enabled by default, and they seem to cause no problems, does the feature even need a name? The release notes could say something like "extended type information is produced for out-of-scope variables beginning with an underscore" or similar. Is it very important that users can specify -XNoTypeHoles?


On Jan 14, 2014, at 11:33 AM, Austin Seipp <austin at well-typed.com> wrote:

> At the very least, Type(d)Holes would never appear explicitly since it
> would be enabled by default. But it might be turned off (but I don't
> know who would do that for the most part.) Cabal at least might still
> need an update.
> In any case, Herbert basically summed it up: the time window is kind
> of close, and we would need to re-release/redeploy a few things most
> likely. I really think it mostly depends on the Cabal team and what
> their priorities are. I've CC'd Duncan and Johan for their opinions.
> On Tue, Jan 14, 2014 at 10:27 AM, Herbert Valerio Riedel <hvr at gnu.org> wrote:
>> Hi,
>> On 2014-01-14 at 17:14:51 +0100, David Luposchainsky wrote:
>>> On 14.01.2014 17:07, Austin Seipp wrote:
>>>> We probably won't change the name right now however. It's already
>>>> been put into Cabal (as a recognized extension,) so the name has
>>>> propagated a slight bit. We can however give it a new name and
>>>> deprecate the old -XTypeHoles in the future. Or, we could change
>>>> it, but I'm afraid it's probably a bit too late in the cycle for
>>>> other devs to change.
>>> Removing a name later on is more time-consuming, with or without
>>> deprecation. People get used to the "wrong" name and stop caring, but
>>> I can already picture the "type holes are really typed holes"
>>> discussions on IRC. I'm strongly in favour of introducing the new name
>>> (and the deprecation for the synonym) as early as possible. This
>>> change should not be very extensive anyway, so why not slip it in?
>> Well, as Austin hinted at, this would also require a Cabal-1.18.x
>> release in time for the final 7.8, and a recompile of Hackage to pick it
>> up so that people can start using the new 'TypedHoles' token in their
>> .cabal files... so there's a bit of coordination required to make this
>> happen in a timely manner... Or put differently, somebody has to care
>> enough to invest some time and pull this through :-)
>> Cheers,
>>  hvr
> -- 
> Regards,
> Austin Seipp, Haskell Consultant
> Well-Typed LLP, http://www.well-typed.com/
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