November 2021 - ghc-steering-committee

Please review #451: Sized literals proposal; Shepherd: Simon M
by Richard Eisenberg 23 Apr '22

23 Apr '22

Dear Committee, This is your interim secretary speaking: Sized literals proposal, proposing syntax for literals for the new sized primitive numeric types, has been proposed by Sylvain Henry. https://github.com/ghc-proposals/ghc-proposals/pull/451 https://github.com/hsyl20/ghc-proposals/blob/sized-literals/proposals/0000-… I propose Simon M as the shepherd. Please guide us to a conclusion as outlined in https://github.com/ghc-proposals/ghc-proposals#committee-process Thanks, Richard

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#425: invisible binders in type declarations; rec: accept
by Richard Eisenberg 07 Apr '22

07 Apr '22

Hi all, I am the shepherd for proposal #425, https://github.com/ghc-proposals/ghc-proposals/pull/425, proposing to add invisible binders in type declarations. The main payload of the proposal is to allow definitions like > data Proxy @k (a :: k) = Proxy instead of today's > data Proxy (a :: k) = Proxy which has no explicit binding site for k. This new syntax solves a number of smallish syntax conundra, as very well outlined in the proposal. In addition, the proposal includes two small unrelated tweaks to the syntax of type family instances; these are points (6) and (7) in the proposal. Both changes will break some obscure (but still realistic, knowing Haskell) programs, but both fixes are backward compatible. --- I recommend acceptance. The proposal is motivated nicely (do check out the examples) and solves a real problem. The new syntax fits in with other similar features. The small cleanups to existing syntax will lead to better error messages. The one drawback, as I see it, is that this proposal includes point (5), which is a breaking change to the way type synonyms work. Right now, we can say > type P = (Proxy :: k -> Type) and GHC will infer P :: forall k. k -> Type. Under this proposal, you would have to write > type P @k = (Proxy :: k -> Type) bringing k into scope explicitly. The fix is not backward compatible, and so I think this proposal should come with a migration strategy, where we warn about the former version for some releases before banning it. (Continuing to support it is possible, but it's very awkward to have a variable mentioned only in a synonym's right-hand side.) Sorry for the delay in producing this recommendation! Richard

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Please review #392: Clarify modifiers design principle, Shepherd: Alejandro
by Joachim Breitner 28 Jan '22

28 Jan '22

Dear Committe, Clarify modifiers design principle has been proposed by Richard https://github.com/ghc-proposals/ghc-proposals/pull/392 This is an amendmend to #370, see the PR description for links to diffs etc. I propose Alejandro as the shepherd, as he shepherded #370 before. 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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Please review #452: Articulate principles for GHC evolution; Shepherd: Simon PJ
by Richard Eisenberg 14 Jan '22

14 Jan '22

Dear Committee, This is your interim secretary speaking: Articulate principles for GHC evolution, proposing a new "principles" document to be added to the proposals repo, has been proposed by me. https://github.com/ghc-proposals/ghc-proposals/pull/452 https://github.com/goldfirere/ghc-proposals/blob/principles/principles.rst I propose Simon PJ as the shepherd, as this is something of a meta-proposal, appropriate for shepherding by our chair. Please guide us to a conclusion as outlined in https://github.com/ghc-proposals/ghc-proposals#committee-process <https://github.com/ghc-proposals/ghc-proposals#committee-process> Thanks, Richard

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Please review #319: NoFallibleDo proposal, Shepherd: Eric Seidel
by Joachim Breitner 08 Jan '22

08 Jan '22

Dear Committee, this is your secretary speaking: NoFallibleDo proposal has been proposed by Cale https://github.com/ghc-proposals/ghc-proposals/pull/319 https://github.com/obsidiansystems/ghc-proposals/blob/no-fallible-do/propos… I propose Eric Seidel as the shepherd. 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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#433: the Unsatisfiable constraint; recommendation: accept
by Tom Harding 08 Dec '21

08 Dec '21

Hi all, Since I last emailed the committee, Adam has split the proposal into two parts: one for `Unsatisfiable` and one for `Warning`. I think I’m right in saying that everyone who has voiced an opinion has been in favour of the `Unsatisfiable` half, so if no one has any further thoughts, I suggest we accept this half and continue discussing `Warning` later on. Thanks, Tom

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Local module proposal on hiatus
by Spiwack, Arnaud 22 Nov '21

22 Nov '21

Dear all, Richard has decided to stop working on the local module proposal [ https://github.com/ghc-proposals/ghc-proposals/pull/283#issuecomment-974382… ]. Just as I was about to say that we ought to accept it unless a strong opposition was voiced within the next two weeks. What's left to do, as far as anyone can tell, is address two minor technical points (there may be other corner cases that have been missed: it's an ambitious proposal after all; but it's looking like it's standing on firm ground). I've stated previously that I care a lot about this proposal. Unfortunately, I currently don't have time to take care of the proposal myself. I may revisit this decision in 2022 (which, fortunately, is rather soon), depending on how my schedule changes. But until then, unless someone steps up, I'll mark the proposal as dormant. Best, Arnaud

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Away from a laptop
by Joachim Breitner 10 Nov '21

10 Nov '21

Dear committee, I’ll be away from my laptop for a few weeks from Monday on, and might be slow to do my secretary duties, and some things (like merging a proposal with updating the metadata and possibly converting from .md to .rst) are quite unwieldy to do just on a phone. If something can’t or should not wait, I’d be grateful if others could cover for me. Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Proposal #281: Visible "forall" in terms; rec: accept
by Richard Eisenberg 01 Nov '21

01 Nov '21

Hi committee, Proposal #281 has been submitted for our consideration. Proposal PR: https://github.com/ghc-proposals/ghc-proposals/pull/281 <https://github.com/ghc-proposals/ghc-proposals/pull/281> Proposal text: https://github.com/int-index/ghc-proposals/blob/visible-forall/proposals/00… <https://github.com/int-index/ghc-proposals/blob/visible-forall/proposals/00…> The text of the proposal is long and detailed, but do not be daunted: it is simpler in practice than it appears. The main payload of the proposal is: Introduce a new extension -XRequiredTypeArguments. With this extension enabled, the `forall ... ->` syntax, currently in existence in kinds, is now available in types (of ordinary functions). This means that function definitions and call sites are sometimes required to write a type argument. The type argument is *not* preceded by @ or any other syntactic marker. This is useful for defining what would otherwise be ambiguous types. Example: > sizeof :: forall a -> Sizeable a => Int > sizeof = ... > > intWidth = sizeof Int There are further examples and motivation in the proposal. The rest of the proposal is simply about dealing with odd corner cases that come up with the main payload. In particular, mixing types in with terms with no syntactic signifier means that we must be careful about parsing and namespaces. If a type argument is written in the syntax that is shared between types and terms (including function application!) and uses identifiers in scope in only one of the two namespaces, nothing unusual can be observed. But, of course, there are corner cases. Here are some of the salient details: - Define type-syntax and term-syntax, where the choice of syntax is always driven by syntactic markers, such as :: or @. See the dependent types proposal <https://github.com/goldfirere/ghc-proposals/blob/dependent-types/proposals/…> for more details. Parsing and name-resolution are controlled by whether a phrase is in type-syntax or term-syntax. For name resolution, if a lookup fails in the first namespace (the term-level namespace in term-syntax or the type-level namespace in type-syntax), we try the other namespace before failing. - Because term- vs type-syntax is controlled by syntax, a required type argument is in *term*-syntax and gets name-resolved *as a term*. In the absence of punning, this works out fine, but it is possible that a punned identifier will cause confusion. The proposal includes section 4.3 allowing users to write `type` to signify a switch to type-syntax. - The proposal also includes a way to avoid punning for the built-in types with privileged syntax: lists and tuples. This method allows users to specify -XNoListTupleTypeSyntax to disable the list and tuple syntax in types (but still allows it for terms). The proposal also suggests exporting type List = [] from Data.List and other synonyms for tuples from Data.Tuple. --------------- I recommend acceptance. When doing type-level programming, the lack of this feature is strange, leading to ambiguous types and easy-to-forget arguments and easy-to-make type errors. The design space here is difficult, but this proposal is very much in keeping with the design sketch of our recently-accepted #378, in particular its section on this point <https://github.com/goldfirere/ghc-proposals/blob/dependent-types/proposals/…>. I believe the design described here is both backward compatible with what we have today (users who do not use this feature will not notice a difference) and forward compatible with a cohesive design for dependent types. There are several optional pieces: - The `type` herald <https://github.com/int-index/ghc-proposals/blob/visible-forall/proposals/00…>. I am unsure about this one, but others have felt strongly in favor, and I have no reason to object. - Types-in-terms <https://github.com/int-index/ghc-proposals/blob/visible-forall/proposals/00…>. I think this is necessary in order to avoid annoying definitions of type synonyms for one-off usage sites. It is a straightforward extension of the term-level parser to allow previously type-level-only constructs. It is necessary in order for us to achieve the vision of dependent types in #378. The only challenge here is that this requires us to make `forall` an unconditional keyword in terms. This does pose a backward-compatibility problem. I see, for example, that the sbv package exports a function named `forall`, so we may need to think more carefully about how to proceed here -- possibly by guarding the keyword-ness of `forall` behind the extension for some number of transitionary releases. - Lists and Tuples <https://github.com/int-index/ghc-proposals/blob/visible-forall/proposals/00…>. This section describes the -XNoListTupleTypeSyntax extension. I am not convinced that this change needs to be part of this proposal (thinking it belongs more in #270), but I do think we'll need it in the end. Is it OK to export new type synonyms from Data.List and Data.Tuple? Not sure, though I'd like these exported from some central place. What do others think? Thanks, Richard

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