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<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%7Cad300416ae01498db28108d8f2ac9f0f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637526170501682820%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=1wG3lnlZyfF%2FciJhxsb8UCWctNymNqC2rs5lScovvn8%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 <simonpj@microsoft.com>
<br>
<b>Sent:</b> 29 March 2021 13:17<br>
<b>To:</b> ghc-steering-committee@haskell.org<br>
<b>Cc:</b> Simon Peyton Jones <simonpj@microsoft.com><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%7Cad300416ae01498db28108d8f2ac9f0f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637526170501672827%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=YyMVsDwi8WK5mIqnECz%2Bjq3sIG8m1ino5sxiBU9Gs6I%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%7Cad300416ae01498db28108d8f2ac9f0f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637526170501682820%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=1wG3lnlZyfF%2FciJhxsb8UCWctNymNqC2rs5lScovvn8%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%7Cad300416ae01498db28108d8f2ac9f0f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637526170501692814%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=qIzScWWQxoSA5OTVfZxdMeMJimq6tEtp98fGJbmfVZw%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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