[ghc-steering-committee] Recommendation for #378: support the design for dependent types

Tue May 18 18:37:30 UTC 2021

> On May 18, 2021, at 3:47 AM, Spiwack, Arnaud <arnaud.spiwack at tweag.io> wrote:
> 
> Sorry, it's a long read. I'd read previous iterations of the proposal, and the wiki page previously. But the current proposal is yet a different text, I didn't want to opine without a proper reading.

Yes, thank you!

> 
> The proposal is long, but doesn't really make a lot of concrete design choices.

Yes, this is intentional.
> 
> The language, though, is sometimes interesting:
> 
> > By accepting this proposal, the committee reaffirms Haskell's status as an evolving, forward-thinking language, excited to adopt new ideas.

Yes, this was an overstep. I've struck this sentence.

> 
> > There remain a few individuals who appear to remain deeply unconvinced. However, these seem to be a small minority. The reasons they are not convinced appear to be around lack of understanding of the proposal/design and general worry about unintended consequences. I have tried to address both of these, but I do not believe my efforts have been fully successful.

I stand by this claim -- though I can see how the language here might be off-putting. This section is meant to be a summary of the discussion, and this really was a part of the discussion. However, I have replaced this bullet with a narrower one, describing the particular worry about people being forced to use dependent types because of early library adoption.

> 
> This is really not helpful, I don't think that we want to merge the proposal with this sort of language in it.
> 
> I'd add that the following:
> 
> > Many industrial Haskellers came out of the woodwork to support this proposal.
> 
> is rather misleading, since there seem to have been just as many industrial Haskellers which came out opposed to the proposal.

I disagree here. The GitHub ticket has 412 positive emotions, and 3 negative ones. The 412 might be an overcount, because I believe one individual can put multiple emoji on the same ticket, but there are at least 274 individuals in favor. It's true that I don't know how many of these are industrial users, but there were quite a few people who identified as industrial users in support. I actually don't know that any of the detractors identified themselves as industrial users, though I didn't read through all the comment trail to check this.

We don't -- and shouldn't -- operate solely (or primarily) on the basis of popularity, but I think both the emoji expressed and the comment trail suggests that this feature is desired in industry more widely than it is opposed.

Richard

> 
> ---
> 
> In summary: I'm in favour of the proposal, as long as Section 5 (Effect and Interaction) and below, are cleaned of the politically charged language.
> 
> On Thu, May 13, 2021 at 5:09 PM Simon Peyton Jones via ghc-steering-committee <ghc-steering-committee at haskell.org <mailto:ghc-steering-committee at haskell.org>> wrote:
> Friends
> 
> You have now had a month to review my recommendation below, to accept #378: support for dependent types. Here it is once more <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fgoldfirere%2Fghc-proposals%2Fblob%2Fdependent-types%2Fproposals%2F0000-dependent-type-design.rst&data=04%7C01%7Csimonpj%40microsoft.com%7Cc0e29b49960a43b4d7ee08d8fff24512%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637540763362468484%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=K1JBnklN2ztnUyibLJ%2Bv9q8%2BK%2Bg1Sf%2FHDGjwVmj25Mw%3D&reserved=0>
> I have heard
> 
> Support: Joachim, Vitaly, Alejandro, Vlad (plus Richard and myself)
> Against: no one
> But that leaves Tom, Eric, Arnaud, Cale, Simon M, and Iavor who have not expressed an opinion.  Please do!
> 
> Failing further feedback, I’ll accept on Tuesday next week.
> 
> There has been some further discussion on the pull request <https://github.com/ghc-proposals/ghc-proposals/pull/378>, but I don’t think any fundamentally new points have come up.  This is clearly a judgement call, but one I think we should make.  Haskell has always been a research lab – that’s part of what makes it distinctive.  I think we can continue to celebrate that innovation.  But see my email immediately below for what we are and are not accepting.
> 
> Simon
> 
>  
> 
> From: Simon Peyton Jones <simonpj at microsoft.com <mailto:simonpj at microsoft.com>> 
> Sent: 15 April 2021 10:39
> To: ghc-steering-committee at haskell.org <mailto:ghc-steering-committee at haskell.org>
> Cc: Simon Peyton Jones <simonpj at microsoft.com <mailto:simonpj at microsoft.com>>
> Subject: Recommendation for #378: support the design for dependent types
>  
> 
> Dear GHC steering committee
> 
> OK Richard has now revised the “Design for Dependent Types” proposal, and has resubmitted it.  As we asked, it now includes the design sketch that constitutes the direction of travel advocated in the proposal, rather than merely referring to it.
> 
> Here it is once more <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fgoldfirere%2Fghc-proposals%2Fblob%2Fdependent-types%2Fproposals%2F0000-dependent-type-design.rst&data=04%7C01%7Csimonpj%40microsoft.com%7Cc0e29b49960a43b4d7ee08d8fff24512%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637540763362468484%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=K1JBnklN2ztnUyibLJ%2Bv9q8%2BK%2Bg1Sf%2FHDGjwVmj25Mw%3D&reserved=0>
> I propose acceptance.
> 
> Remember:
> 
> We would not be accepting every detail of the design in Section 4 – rather, we expect further specific proposals as we move in the direction described in the proposal.   So we should not debate the fine print of Section 4. 
> We would be accepting that the proposal describes a direction of travel that we are happy with.  That in turn gives people the confidence to invest efforts in those more detailed proposals.  As the “Proposed change specification” says:  “When evaluating new proposals, the GHC committee would consider compatibility with the design sketch below. Generally speaking, new proposals should be forward-compatible with the design sketch; that is, the new features proposed would continue to be at home when surrounded by other dependent-type features.”
> Any views?   Questions of clarification or technical questions belong on the comment stream.
> 
> Thanks
> 
> Simon
> 
> From: ghc-steering-committee <ghc-steering-committee-bounces at haskell.org <mailto:ghc-steering-committee-bounces at haskell.org>> On Behalf Of Simon Peyton Jones via ghc-steering-committee
> Sent: 06 April 2021 13:58
> To: ghc-steering-committee at haskell.org <mailto:ghc-steering-committee at haskell.org>
> Subject: Re: [ghc-steering-committee] Recommendation for #378: support the design for dependent types
>  
> 
> Richard and I have discussed this.
> 
> We concluded that we’d put it back into “Needs revision” status. He’s going to expand it (substantially) to include the proposed design sketch of dependent types on the GHC wiki <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.haskell.org%2Fghc%2Fghc%2F-%2Fwikis%2Fdependent-haskell&data=04%7C01%7Csimonpj%40microsoft.com%7Cc0e29b49960a43b4d7ee08d8fff24512%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637540763362478476%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=C5Ywef9f5MK4jEc2XfmXeZ26YIdJeP0%2F%2BKfGdIhfkYA%3D&reserved=0>.  Then he’ll resubmit in the hope of getting approval of the design in principle, subject to subsequent discussion of the fine detail.
> 
> Simon
> 
>  
> 
> From: Simon Peyton Jones <simonpj at microsoft.com <mailto:simonpj at microsoft.com>> 
> Sent: 29 March 2021 13:17
> To: ghc-steering-committee at haskell.org <mailto:ghc-steering-committee at haskell.org>
> Cc: Simon Peyton Jones <simonpj at microsoft.com <mailto:simonpj at microsoft.com>>
> Subject: Recommendation for #378: support the design for dependent types
>  
> 
> Dear GHC Steering Committee
> 
> I’m recommending acceptance of Proposal #378: Support the design for dependent types <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F378&data=04%7C01%7Csimonpj%40microsoft.com%7Cc0e29b49960a43b4d7ee08d8fff24512%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637540763362478476%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=%2Bf32VqzdL6HgiF436%2FGWPwBl09c1qo%2BAMbgPY6tJfSI%3D&reserved=0>
> As you’ll see, there is a lot of useful context, but the payload is pretty simple
> 
> When evaluating new proposals, the GHC committee would consider compatibility with the proposed design sketch of dependent types on the GHC wiki <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.haskell.org%2Fghc%2Fghc%2F-%2Fwikis%2Fdependent-haskell&data=04%7C01%7Csimonpj%40microsoft.com%7Cc0e29b49960a43b4d7ee08d8fff24512%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637540763362488470%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=1xOofIrHU3rP91mxYwvKnefFqCA5RBHCUUuKHqtdZlo%3D&reserved=0>. Generally speaking, new proposals should be forward-compatible with the design sketch; that is, the new features proposed would continue to be at home when surrounded by other dependent-type features.
> 
> Of course, the committee remains free to revise the design sketch or to accept proposals that encroach upon it (i.e. contradicting this guidance), but such choices should be made explicitly.
> 
> See also the committee's Review Criteria <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2F%23review-criteria&data=04%7C01%7Csimonpj%40microsoft.com%7Cc0e29b49960a43b4d7ee08d8fff24512%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637540763362488470%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=C%2B6VLghDD03q1Qwqwytrp75eAHQtPF%2FB1SveNIKrymA%3D&reserved=0>: put another way, this proposal says that we consider the design sketch alongside other features of today's Haskell when assessing a new proposal's fit with the language.
> 
> Note that compatibility with dependent types is far from the only criterion the committee would use to evaluate a proposal. Other review criteria, such as learnability, clarity of error messages, performance, etc., remain just as ever.
> 
> Any views?  Let’s try to converge rapidly…. the proposal has been substantially refined by a lot of debate.
> 
> Simon
> 
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