We need to add role annotations for 7.8

[Richard Eisenberg]

Well, I'm satisfied now -- again, that was all much easier than I anticipated. Thanks, all!

On Mar 13, 2014, at 4:46 PM, Johan Tibell wrote:

> Tagged and released containers-0.5.5.0.
> 
> 
> On Thu, Mar 13, 2014 at 9:26 PM, Austin Seipp <austin at well-typed.com> wrote:
> That would be ideal if you don't mind, so we can go ahead and merge it
> and get that out of the way (vector etc can come soon after, but we
> don't ship that in the GHC distributions, so it's less of a problem).
> 
> On Thu, Mar 13, 2014 at 3:22 PM, Johan Tibell <johan.tibell at gmail.com> wrote:
> > Applied. Do you need a containers release ASAP so it can ship with 7.8?
> >
> >
> > On Thu, Mar 13, 2014 at 9:11 PM, Richard Eisenberg <eir at cis.upenn.edu>
> > wrote:
> >>
> >> Patch attached. I only needed Map and Set -- the others are inferred. I
> >> guess this was simpler than I thought. :)
> >>
> >> Richard
> >>
> >>
> >> On Mar 13, 2014, at 2:49 PM, Johan Tibell <johan.tibell at gmail.com> wrote:
> >>
> >> If you send a pull request for containers I'll merge it and make a
> >> release. It needs to be backwards compatible with the last 3 major GHC
> >> releases. I think we need to bump the minor version number so people can
> >> reliable write dependency bounds to depend on the role being there (as that
> >> might be the difference between code compiling or not).
> >>
> >> Here's a guess which params should be representational:
> >>
> >> Map k v -- k: nominal, v: represententional
> >> Set a -- k: nominal
> >> IntMap v -- v: represententional
> >> Sequence a -- a: represententional
> >> Tree a -- a: represententional
> >>
> >>
> >> On Thu, Mar 13, 2014 at 7:41 PM, Richard Eisenberg <eir at cis.upenn.edu>
> >> wrote:
> >>>
> >>> Hi libraries, Johan, Edward,
> >>>
> >>> tl;dr: We really should add role annotations to the libraries that ship
> >>> with GHC 7.8.
> >>>
> >>> In November, I sent this out:
> >>> http://www.haskell.org/pipermail/libraries/2013-November/021707.html
> >>> It got several good responses. Some time later, Joachim and I noticed
> >>> that no action was taken, so we made a bug report, #8718, with a milestone
> >>> of 7.8.1. I believe we both assumed that would take care of it. However,
> >>> Simon PJ and I were surprised earlier this week to discover that Map and Set
> >>> still do not have role annotations. Perhaps the GHC Trac isn't the right
> >>> place for libraries issues, but posting here didn't quite work, so that
> >>> seemed like the logical next step.
> >>>
> >>> In any case, now that we have the ability to prevent abuses of datatypes
> >>> like Map and Set through erroneous use of GeneralizedNewtypeDeriving (and
> >>> the new `coerce`), we should take advantage of this fact for 7.8. See my
> >>> earlier email for a full explanation.
> >>>
> >>> Possibly folks' unfamiliarity with roles are in part to blame for not
> >>> adding these role annotations. I am happy to help sort out what goes where.
> >>> But, I need to work with someone with an intimate familiarity with the
> >>> libraries themselves to help determine what the correct annotations are. For
> >>> example, Map's first parameter should be nominal (its Ord instance is very
> >>> relevant) but its second should be representational (there are no particular
> >>> invariants related to the values of a map). Map is straightforward in this
> >>> respect; other types probably aren't. Furthermore, I don't have anywhere
> >>> near a complete list of what even needs attention. (It should be any type
> >>> abstractly exported from a library.)
> >>>
> >>> Can someone help? I've included Johan as the most recent uploader of
> >>> `containers` and Edward as the head of the core libraries committee.
> >>>
> >>> Thanks!
> >>> Richard
> >>
> >>
> >>
> >>
> >
> >
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> >
> 
> 
> 
> --
> Regards,
> 
> Austin Seipp, Haskell Consultant
> Well-Typed LLP, http://www.well-typed.com/
> 

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