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<p class="MsoNormal">Dear GHC steering committee<o:p></o:p></p>
<p class="MsoNormal">OK Richard has now revised the “Design for Dependent Types” proposal, and has resubmitted it. As we asked, it now
<i>includes</i> the design sketch that constitutes the direction of travel advocated in the proposal, rather than merely
<i>referring</i> to it.<o:p></o:p></p>
<p class="MsoNormal"><a href="https://github.com/goldfirere/ghc-proposals/blob/dependent-types/proposals/0000-dependent-type-design.rst">Here it is once more</a><o:p></o:p></p>
<p class="MsoNormal">I propose acceptance.<o:p></o:p></p>
<p class="MsoNormal">Remember:<o:p></o:p></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:2.5pt;mso-list:l0 level1 lfo1">We
<b>would not</b> 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.
<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:2.5pt;mso-list:l0 level1 lfo1">We
<b>would</b> 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.”<o:p></o:p></li></ul>
<p class="MsoNormal">Any views? Questions of clarification or technical questions belong on the comment stream.<o:p></o:p></p>
<p class="MsoNormal">Thanks<o:p></o:p></p>
<p class="MsoNormal">Simon<o:p></o:p></p>
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<p class="MsoNormal" style="margin:0cm"><b><span lang="EN-US" style="mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="mso-fareast-language:EN-GB"> ghc-steering-committee <ghc-steering-committee-bounces@haskell.org>
<b>On Behalf Of </b>Simon Peyton Jones via ghc-steering-committee<br>
<b>Sent:</b> 06 April 2021 13:58<br>
<b>To:</b> ghc-steering-committee@haskell.org<br>
<b>Subject:</b> Re: [ghc-steering-committee] Recommendation for #378: support the design for dependent types<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Richard and I have discussed this.<o:p></o:p></p>
<p class="MsoNormal">We concluded that we’d put it back into “Needs revision” status. He’s going to expand it (substantially) to include
<i><a href="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%7C1b7abe0682c0408df2f708d8f8fbeb5f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637533108900934303%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=nucS4608uGvDJd6ki1pJCMfwCP1jlbxVls4IaoJmu84%3D&reserved=0">the
proposed design sketch of dependent types on the GHC wiki</a>. </i>Then he’ll resubmit in the hope of getting approval of the design in principle, subject to subsequent discussion of the fine detail.<o:p></o:p></p>
<p class="MsoNormal">Simon<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin:0cm"><b><span lang="EN-US" style="mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="mso-fareast-language:EN-GB"> Simon Peyton Jones <<a href="mailto:simonpj@microsoft.com">simonpj@microsoft.com</a>>
<br>
<b>Sent:</b> 29 March 2021 13:17<br>
<b>To:</b> <a href="mailto:ghc-steering-committee@haskell.org">ghc-steering-committee@haskell.org</a><br>
<b>Cc:</b> Simon Peyton Jones <<a href="mailto:simonpj@microsoft.com">simonpj@microsoft.com</a>><br>
<b>Subject:</b> Recommendation for #378: support the design for dependent types<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Dear GHC Steering Committee<o:p></o:p></p>
<p class="MsoNormal">I’m recommending acceptance of Proposal #378: <a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F378&data=04%7C01%7Csimonpj%40microsoft.com%7C1b7abe0682c0408df2f708d8f8fbeb5f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637533108900944303%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=zmz9Iywt1EuiJdFKzuGaxLI5Zeu3ZnqNYwG7MoZTmpA%3D&reserved=0">
Support the design for dependent types</a><o:p></o:p></p>
<p class="MsoNormal">As you’ll see, there is a lot of useful context, but the payload is pretty simple<o:p></o:p></p>
<p style="margin-left:36.0pt"><i>When evaluating new proposals, the GHC committee would consider compatibility with
<a href="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%7C1b7abe0682c0408df2f708d8f8fbeb5f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637533108900954303%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=nPnYN%2BIZYLORpnhxp6MDygTa83E25HhvzoLxlE3uc0s%3D&reserved=0">
the proposed design sketch of dependent types on the GHC wiki</a>. 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.<o:p></o:p></i></p>
<p style="margin-left:36.0pt"><i>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.<o:p></o:p></i></p>
<p style="margin-left:36.0pt"><i>See also the committee's <a href="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%7C1b7abe0682c0408df2f708d8f8fbeb5f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637533108900954303%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=jSLVnZCggbNtM8QkU26f2WaulvymUb%2BEaGIO6E5%2B8%2FU%3D&reserved=0">
Review Criteria</a>: 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.<o:p></o:p></i></p>
<p style="margin-left:36.0pt"><i>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.<o:p></o:p></i></p>
<p class="MsoNormal">Any views? Let’s try to converge rapidly…. the proposal has been substantially refined by a lot of debate.<o:p></o:p></p>
<p class="MsoNormal">Simon<o:p></o:p></p>
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