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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">(Writing to the committee rather than polluting the DT proposal thread.)<o:p></o:p></span></p>
<p style="margin-left:36.0pt">We have a bullet “Does not create a language fork” in the
<a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%23review-criteria&data=04%7C01%7Csimonpj%40microsoft.com%7C2d39084e129047d031f508d8e3044dca%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637508954935323802%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=F0fX%2BB%2BjH7xfJWoiYxNOfJRFvo6vix6HhwID5%2FXt1EU%3D&reserved=0">
review criteria</a>. I treat it like the other criteria, a fork-like proposal is a red flag, but not an automatic reject.<o:p></o:p></p>
<p class="MsoNormal" style="-webkit-text-size-adjust:none"><span style="mso-fareast-language:EN-US">This relates back to our earlier conversation about proposal properties. Eric suggested:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo2"><b><span style="mso-fareast-language:EN-US">Backward compatibility</span></b><span style="mso-fareast-language:EN-US">. Does an extension *<b>expand</b>* the language or *<b>change</b>*
it? In other words, does an extension strictly accept more programs than before, or can it change the meaning of existing programs, or even reject previously valid programs?<o:p></o:p></span></li></ul>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo2"><b><span style="mso-fareast-language:EN-US">Plausible default.
</span></b><span style="mso-fareast-language:EN-US">Do we expect the extension to eventually be on-by-default (in GHCxxxx) and effectively disappear, or will it continue to be opt-in? -XStrict or -XRebindableSyntax are examples of an extension that we want,
but that are not plausible defaults. <o:p></o:p></span></li></ul>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo2"><b><span style="mso-fareast-language:EN-US">Localised</span></b><span style="mso-fareast-language:EN-US">. Is an extension *<b>contained</b>* within a module or is it *<b>infectious</b>*?
Does my choice of extensions when writing a module affect which extensions downstream clients must enable? (I would say most extensions are contained, e.g. you can apply a type family without enabling TypeFamilies or match on a pattern synonym without enabling
PatternSynonyms. However, you cannot call a function that takes an implicit parameter without enabling ImplicitParams.)<o:p></o:p></span></li></ul>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Reading our “fork-like” criterion, it seems to be saying “it’s fork-like if it is not a plausible default (in the above sense), and fork-like is bad”. But as -XStrict and -XRebindableSyntax show,
not being a plausible default isn’t necessarily bad. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Do we want to revise our language in the criteria?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Eric Seidel <notifications@github.com>
<br>
<b>Sent:</b> 09 March 2021 14:05<br>
<b>To:</b> ghc-proposals/ghc-proposals <ghc-proposals@noreply.github.com><br>
<b>Cc:</b> Simon Peyton Jones <simonpj@microsoft.com>; Assign <assign@noreply.github.com><br>
<b>Subject:</b> Re: [ghc-proposals/ghc-proposals] Support ergonomic dependent types (#378)<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p>Do we have a write up of what it means to be fork-like? Or what role the fork-like property plays in our deliberations?<o:p></o:p></p>
</blockquote>
<p>We have a bullet “Does not create a language fork” in the <a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%23review-criteria&data=04%7C01%7Csimonpj%40microsoft.com%7C2d39084e129047d031f508d8e3044dca%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637508954935323802%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=F0fX%2BB%2BjH7xfJWoiYxNOfJRFvo6vix6HhwID5%2FXt1EU%3D&reserved=0">
review criteria</a>. I treat it like the other criteria, a fork-like proposal is a red flag, but not an automatic reject.<o:p></o:p></p>
<p style="-webkit-text-size-adjust:none"><span style="font-size:12.0pt;color:#666666">—<br>
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