<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Done.<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Apr 17, 2018, at 7:09 PM, Simon Peyton Jones <<a href="mailto:simonpj@microsoft.com" class="">simonpj@microsoft.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class="">Would it be worth revising the proposal to incorporate the thinking in this thread, including the answers to Iavor’s questions?<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class="">Simon<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class=""><o:p class=""> </o:p></span></div><div style="border-style: none none none solid; border-left-width: 1.5pt; border-left-color: blue; padding: 0cm 0cm 0cm 4pt;" class=""><div class=""><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(225, 225, 225); padding: 3pt 0cm 0cm;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span lang="EN-US" class="">From:</span></b><span lang="EN-US" class=""><span class="Apple-converted-space"> </span>ghc-steering-committee <<a href="mailto:ghc-steering-committee-bounces@haskell.org" class="">ghc-steering-committee-bounces@haskell.org</a>><span class="Apple-converted-space"> </span><b class="">On Behalf Of<span class="Apple-converted-space"> </span></b>Richard Eisenberg<br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>17 April 2018 20:22<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span>Iavor Diatchki <<a href="mailto:iavor.diatchki@gmail.com" class="">iavor.diatchki@gmail.com</a>><br class=""><b class="">Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:ghc-steering-committee@haskell.org" class="">ghc-steering-committee@haskell.org</a>; Joachim Breitner <<a href="mailto:mail@joachim-breitner.de" class="">mail@joachim-breitner.de</a>><br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>Re: [ghc-steering-committee] Proposal: Embrace Type in Type<o:p class=""></o:p></span></div></div></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hi Iavor,<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">See my answers below.<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><br class=""><br class=""><o:p class=""></o:p></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;" class=""><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">On Apr 17, 2018, at 2:23 PM, Iavor Diatchki <<a href="mailto:iavor.diatchki@gmail.com" style="color: purple; text-decoration: underline;" class="">iavor.diatchki@gmail.com</a>> wrote:<o:p class=""></o:p></div></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hello,<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">I have a couple of pragmatic questions:<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">1. To "fix" my code so that it is compatible with this change I need to do the following:<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> 1. Whenever I have kind signatures mentioning `*`, replace `*` with `Type`<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> 2. Import `Data.Kind(Type)`<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> 3. Resolve conflicts involving existing datatypes named `Type`.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">2. If my code has all of the properties below, then it will break as soon as this change is adopted, so I have to fix it in some way straight away:<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> 1. uses `*` is a binary type operator, and<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> 2. uses `*` in kind signatures, and<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> 3. uses the `PolyKinds` language extension.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">3. If my code does not have the properties in (2) but uses `*` in kind signatures, it will continue to work for 2 GHC releases, but then it will break, so I should do (1) sometime before.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Is my understanding correct?<o:p class=""></o:p></div></div></div></div></div></blockquote><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Not quite.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">First off, this proposal *does not* propose deprecating *. Earlier versions may have, but that's no longer the case. There is no concrete plan to remove * at any point in the future. Any movement to do so would be years in the future, I imagine.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">In point (1), "compatible" is unclear. I think you mean "compatible forever" as opposed to "compatible today". The changes you suggest in (1) are what you would have to do if we ever decide to deprecate *.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">For point (2), the conditions are slightly different than what you write. They should be<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> a. enables -XTypeOperators<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> b. uses `*` in kind signatures<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Modules that have these features will have to make an immediate change. They could either do the changes under your point (1) or enable -XStarIsType.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">The only part of this proposal that mentions something that will happen in 2 releases is that -XTypeOperators will stop implying -XNoStarIsType in two releases. That particular aspect of this is up for debate, of course.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Richard<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><br class=""><br class=""><o:p class=""></o:p></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;" class=""><div class=""><div class=""><div class=""><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">-Iavor<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div></div></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">On Mon, Apr 16, 2018 at 10:46 AM Joachim Breitner <<a href="mailto:mail@joachim-breitner.de" style="color: purple; text-decoration: underline;" class="">mail@joachim-breitner.de</a>> wrote:<o:p class=""></o:p></div></div><blockquote style="border-style: none none none solid; border-left-width: 1pt; border-left-color: rgb(204, 204, 204); padding: 0cm 0cm 0cm 6pt; margin-left: 4.8pt; margin-right: 0cm;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hi,<br class=""><br class="">Am Montag, den 16.04.2018, 11:55 -0400 schrieb Richard Eisenberg:<br class="">> An alternative that hasn't been suggested so far is to have<br class="">> -XStarIsType control the pretty-printer as well as the parser. Simon<br class="">> PJ and I discussed this this morning, thinking it was a good idea.<br class="">> Upon further consideration, my preference would be to bite the bullet<br class="">> and just switch to printing Type always, but I'm not really against<br class="">> the print-*-with-XStarIsType idea.<br class=""><br class="">I’m with Simon here. We have, I believe, precedence where error<br class="">messages are affected by the language extension in scope, so this might<br class="">satisfy the principle of least surprise, and also cause the least<br class="">contention among our users.<br class=""><br class="">We can still apply this rule when `-XNoStarIsType`:<br class=""><br class="">> One slightly separate question is what to print. The proposal<br class="">> currently suggests to print Type. There was concern in this thread<br class="">> that it would be printed fully-qualified, but I like Joachim's<br class="">> suggestion in the last known email in this thread to special-case<br class="">> printing of Type; even if it's not imported, it would print as Type,<br class="">> not Data.Kind.Type. (Unless some other Type were in scope.) It is<br class="">> also easy to teach GHC to print a bespoke warning when a user writes<br class="">> Type when it is out of scope, telling them to import Data.Kind.<br class=""><br class="">The proposal currently does not state which modules export Type. I can<br class="">infer from the text that it is Data.Kind, but this could be made<br class="">explicit. Also, the proposal should state whether it is re-exported<br class="">from Prelude or not (I assume it is not).<br class=""><br class="">Cheers,<br class="">Joachim<br class=""><br class="">--<span class="Apple-converted-space"> </span><br class="">Joachim Breitner<br class=""> <span class="Apple-converted-space"> </span><a href="mailto:mail@joachim-breitner.de" target="_blank" style="color: purple; text-decoration: underline;" class="">mail@joachim-breitner.de</a><br class=""> <span class="Apple-converted-space"> </span><a href="http://www.joachim-breitner.de/" target="_blank" style="color: purple; text-decoration: underline;" class="">http://www.joachim-breitner.de/</a><br class="">_______________________________________________<br class="">ghc-steering-committee mailing list<br class=""><a href="mailto:ghc-steering-committee@haskell.org" target="_blank" style="color: purple; text-decoration: underline;" class="">ghc-steering-committee@haskell.org</a><br class=""><a href="https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee" target="_blank" style="color: purple; text-decoration: underline;" class="">https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee</a><o:p class=""></o:p></div></blockquote></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">_______________________________________________<br class="">ghc-steering-committee mailing list<br class=""><a href="mailto:ghc-steering-committee@haskell.org" style="color: purple; text-decoration: underline;" class="">ghc-steering-committee@haskell.org</a><br class=""><a href="https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee" style="color: purple; text-decoration: underline;" class="">https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee</a></div></div></blockquote></div></div></div></div></div></blockquote></div><br class=""></body></html>