February 2023 - ghc-steering-committee

Language Extension Policy – Round 1
by Arnaud Spiwack 30 Mar '23

30 Mar '23

Dear all, I am to shepherd the making of our language extension policy, working off our draft document [ https://docs.google.com/document/d/1_-hPh8BRhKNlzM0dC1IRSmjCqPym9mXx9NjC7jU… ]. As a prelude to my introduction, I first want to apologise for taking that long to get back to this subject, time has, I'm afraid, gotten away from me. Part of the reason, though, is that we've been pulling in many directions, and I felt it difficult to find a path toward consensus among all that. In the time since I accepted the task, I have therefore spent a lot of time reading through the entire document multiple time, to try and identify the points where we agree and the points where we diverge. And try to build a methodology. If you go to the document, you'll see that I've separated out our notes after a horizontal line. I will grow the document above the line with decisions from this mailing list. Hopefully, the process will make sure that we are in broad agreement that the text does reflect our collective position. The way I'm going to proceed is to organise votes. Or maybe they should rather be seen as surveys. They'll have a bunch of questions, pertaining to bits of the documents that I want us to converge on. I'll extract a broad consensus from this survey, and use it to copy language in the document. I intend to give about a week for each survey to complete (conveniently, I'll be very far from a computer for the next week, so I'll be able to tally the results when I come back). It's going to take a while, but it's a very difficult, and sensitive, subject. --- For this first round, I want us to focus on the categorisation of language extensions as proposed by Richard and Simon M (sections 2.1 and 2.3, respectively, of our draft notes). As I feel that we will need to have these categories identified in order to discuss the later points. Here are the categories that are common to both (consult the document for more details): 1. Extensions that are either in GHC20xx or could be part of a future GHC20xx (e.g. GADTs) 2. Experimental language features (e.g. LinearTypes) 3. Extensions that allow module-wide violation of some general principle that holds elsewhere (e.g. OverlappingInstances) 4. Extensions that allow access to deprecated features (e.g. DatatypeContexts) 5. Extensions that should be compiler flags, which do not actually change the accepted language (e.g. Safe) Richard adds another category 6. Extensions that change the semantics of existing constructs (e.g. OverloadedStrings); as opposed to most extensions, which create new syntax for the new feature. Richard's reasoning is twofold 1/ he doesn't believe that they should be candidate for inclusion in GHC20xx 2/ he believes that they are problematic for the same sort of reason as we've used to argue against fork-like behaviour: that to understand the meaning of a piece of code you need to know what language extensions have been loaded in the file. Simon M adds another category 7. Extensions for specialised use-cases (e.g. MagicHash, UnboxedTuples) Simon's reasoning is that these should not be part of GHC20xx. At the very least they are not intended to. But they do extend the language, like 1, and unlike 5. Hence they deserve to be categorised separately from both. It is worth noting that Richard classifies Strict as a 6 and Simon M classifies Strict as a 7. Now the survey. Keeping in mind that the goal of this categorisation is to classify the extensions that currently exist, without judgement on whether we want to have things in these categories or not: Q1: Are all the categories 1–5 relevant? If you would like to remove some categories, which and why (free form)? Q2: Is category 6 relevant? Q2.Y: If you found category 6 to be relevant: should it be its own category, or should it be a subcategory of 1? Q2.N: If you found category 6 not to be relevant, in which category would you classify OverloadedStrings? What about PolyKinds? Q3: Is category 7 relevant? Q3.Y: If you found category 7 to be relevant: should it be its own category or should it be a subcategory of 5? Q3.N: If you found category 7 not to be relevant: in which category would you classify MagicHash? What about UnboxedTuples? Q4: In which category would you classify Strict? Q5: Is there any category that you feel is missing from the list? If so, please argue (free form). Best, Arnaud

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Please review #536: Type-level literals as a separate language extension, Shepherd: Vlad
by Joachim Breitner 06 Mar '23

06 Mar '23

Dear Committee, Ross Paterson proposes Type-level literals as a separate language extension https://github.com/ghc-proposals/ghc-proposals/pull/536 https://github.com/RossPaterson/ghc-proposals/blob/literals/proposals/0000-… I suggest Vlad to shepherd this, as he has already engaged with it on Github. Please guide us to a conclusion as outlined in https://github.com/ghc-proposals/ghc-proposals#committee-process Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Please review #512: NoFieldSelectors as datatype annotation, Shepherd: Baldur
by Joachim Breitner 02 Mar '23

02 Mar '23

Dear Committee, NoFieldSelectors as datatype annotation have been proposed by Matt Parsons https://github.com/ghc-proposals/ghc-proposals/pull/512 https://github.com/parsonsmatt/ghc-proposals/blob/matt/field-selectors-scop… I suggest Baldur to shepherd this proposal. Please guide us to a conclusion as outlined in https://github.com/ghc-proposals/ghc-proposals#committee-process Thanks, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Call for votes: Shall we have GHC2023
by Joachim Breitner 10 Feb '23

10 Feb '23

Hi Committee, as ~threatened~ announced, I’m calling for a vote on whether we should proceed to define the next GHC20xx _now_, as GHC2023, or wait for a year. Judging from the silence around the PR for GHC2023 I deduce that the appetite for GHC2023 is generally low, and will not bother you with complicated looking questions about which extensions might make GHC2023 worth it in an attempt to parallelize the “whether” with the “what”. Instead, please cast your vote until Apri 5 (but preferrably earlier) on the question: Should we proceed towards GHC2023? (If yay wins we’ll refine #559 and vote on that. If nay wins, I’ll stay quiet until next fall.) I am intentionally not asking for a fixed cadence at this point. We have made but one release so far, and it seems presumptious to try to predict what makes most sense next year, or the next four years to come. (I’ll follow up with my vote and justification separately.) Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Proposal #556 recommendation: accept
by Richard Eisenberg 10 Feb '23

10 Feb '23

Hi all, Vlad has proposed https://github.com/ghc-proposals/ghc-proposals/pull/556, an amendment to recently accepted proposal #448 on scoped type variables. It adds a nuance saying that f (MkT @(a :: <<here>>)) = ... should have the same scoping behavior as f (MkT (x :: <<here>>)) = ... Note that the first is a kind signature of a visible-type-application-in-a-pattern, while the second is a pattern signature. The intended scoping rule says that the use of an in-scope type variable in these positions is an occurrence, while the use of an out-of-scope type variable brings that variable into scope. Vlad's proposal corrects the phrasing in the original proposal that aligns the treatment of the kind signature with the type it is describing, forbidding e.g. the use of a repeated variable in the kind signature. Vlad's amendment makes the proposal what I had intended when I wrote #448; I strongly recommend acceptance. I think this is a small tweak of a technical detail buried in #448 and hope this does not cause widespread debate. I will accept this proposal in a week if I don't hear objections. Thanks! Richard

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#515 Relaxing HasField constraints, reassigned to Moritz
by Joachim Breitner 09 Feb '23

09 Feb '23

Hi committee, with Tom stepping down, we have to re-assign this proposal: #515 Relaxing HasField constraints https://github.com/ghc-proposals/ghc-proposals/pull/515 https://github.com/ocharles/ghc-proposals/blob/hasfield/proposals/0000-hasf… It was submitted in August 2022, and Tom recommended acceptance. Richard raised technical issues with it. I’d like to assign it to Adam, but he’s a co-author… So in best tradition of our committee, I’ll assign this to Moritz. Moritz, can you help drive the discussion, here and/or on Github? Maybe the proposal needs to be revised, based on Richard’s objections? Then you can label it as “needs-revision” until the authors come back to you. Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Thanks, Tom!
by Joachim Breitner 09 Feb '23

09 Feb '23

Hi, Tom told me that it’s time for him to step down. Thanks, Tom, for your service on the committee in the last three years, and don’t be a stranger to GHC! (Tom was an “expiring member” anyways since January, but we are still 10 members strong, so this does not trigger a new call for nominations. The next regular call for nomination will happen next spring when Richard’s, Vlad’s and my terms expire.) Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Welcome Moritz Angermann
by Joachim Breitner 08 Feb '23

08 Feb '23

Hello everybody, the committee welcomes Moritz Angermann as our newest member! Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Fast tracked amendment: Warning category syntax (#576)
by Joachim Breitner 05 Feb '23

05 Feb '23

Hi, implementation work on warning categories (#541) shows that the implementation would be much simpler if the category was lexed as a string literal, and Adam wants to amend his warning category proposal to the syntax {-# WARNING in "x-some-category" "message" #-} This amendment is at https://github.com/ghc-proposals/ghc-proposals/pull/576. This seems to be changing a minor aspect of the original proposal and implementation is ready, so I think we can fast-track accepting this. If you disagree with this process please complain until the end of the week (Sun Feb 5). Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Fast tracked amendment: No #. label (#573)
by Joachim Breitner 05 Feb '23

05 Feb '23

Hi, implementation work on #170 led to insights that called for small adjustments to the design, namely to remove dot from characters allowed in overloaded labels. The proposal is amended at https://github.com/ghc-proposals/ghc-proposals/pull/573. This should be part of 9.6, so I’d like to fast-track this for acceptance. If you disagree with this process please complain until the end of the week (Sun Feb 5). Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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