This feature has already been proposed:
https://github.com/ghc-proposals/ghc-proposals/pull/196
But the discussion there has stalled. You may want to take a look at the
existing discussion, and if you see a way forward, comment on the proposal (or
open a competing one).
- Vlad
> On 4 Aug 2020, at 20:45, Anselm Schüler (conversations subemail)
> <conversat...@anselmschueler.com> wrote:
>
> Thank you for the nice introduction :) !
> I will check out the GHC proposals site.
> And following Simon’s (I hope addressing with first name is OK) suggestion,
> I’m going to give an outline of the idea.
>
> The idea is to extend type application syntax to enable explicit assignment
> of types to specific type variables.
> For instance, say I have f :: forall a b. (a, b) -> (b, a), and I want to
> apply the type [String] to it. My only option is to do
> f @([String]) :: forall b. ([String], b) -> (b, [String])
> —but what if, instead, I want a function of type forall a. (a, [String]) ->
> ([String], a)?
> I propose the following syntax:
> f @{b = [String]} :: forall a. ([String], b) -> (b, [String])
> This wouldn’t break any existing programs since using record syntax here is
> already disallowed and met with an error message.
> A question is of course the symbol used for assignment (~, =, ::, or ->?).
>
> I hope the code shows up as a monospace font on your end. I used the IBM Plex
> Mono font, which is open-source.
>
> Anselm Schüler
> www.anselmschueler.com
> m...@anselmschueler.com
>
> From: Simon Peyton Jones
> Sent: Tuesday, August 4, 2020 18:44
> To: Richard Eisenberg; "Anselm Schüler (conversations subemail)"
> Cc: ghc-devs@haskell.org
> Subject: RE: Hi. I'm new to this mailing list and have a few questions.
>
> Welcome Anselm. ghc-devs is a very informal mailing list, and we welcome
> newcomers.
>
> For example, I have a feature idea in the back of my mind, which I imagine
> would be easy to implement
>
> What Richard says is right, but you should feel free to fly the kite on this
> list if you want – or on Haskell Café – to get some idea of whether others
> seem warm about the idea, before writing a full proposal.
>
> Simon
>
> From: ghc-devs <ghc-devs-boun...@haskell.org> On Behalf Of Richard Eisenberg
> Sent: 04 August 2020 16:05
> To: "Anselm Schüler (conversations subemail)"
> <conversat...@anselmschueler.com>
> Cc: ghc-devs@haskell.org
> Subject: Re: Hi. I'm new to this mailing list and have a few questions.
>
> Hi Anselm,
>
> Welcome!
>
> A good way of getting used to a list like this one is to wait a little while
> and observe what kind of messages others send; this will give you a feel for
> how the list is used. If you're impatient, you can also check out the
> archives at https://mail.haskell.org/pipermail/ghc-devs/.
>
> As for a feature request: if your feature changes the language GHC accepts
> (most do), the right place to post is at
> https://github.com/ghc-proposals/ghc-proposals. There is a description of how
> to proceed on that page. Proposals submitted there get debated within the
> community and then eventually sent to a GHC Steering Committee for a vote on
> acceptance or rejection. Then, we worry about implementing it. If you have a
> suggestion that does not change the language GHC accepts, you can post an
> Issue at https://gitlab.haskell.org/ghc/ghc/.
>
> I hope this is helpful!
> Richard
>
>
> On Aug 4, 2020, at 8:59 AM, Anselm Schüler (conversations subemail)
> <conversat...@anselmschueler.com> wrote:
>
> First of all, in general, I’m new to mailing lists (as used for discussions)
> in general, so a question about that:
> When subscribed to the mailing list, do you get every message, or are some
> discussions hidden?
>
> Second of all, I’d like to know what kinds of messages are appropriate here.
> I’m not familiar with coding compilers or anything of the like, so I’m
> somewhat afraid of offering unhelpful comments or being just woefully
> underqualified to participate here.
> For example, I have a feature idea in the back of my mind, which I imagine
> would be easy to implement (that might be wrong). Is it alright if I submit
> that here or should I use some other forum?
>
> Thank you in advance for the answers.
>
> Anselm Schüler
> www.anselmschueler.com
> m...@anselmschueler.com
> _______________________________________________
> ghc-devs mailing list
> ghc-devs@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
>
>
> _______________________________________________
> ghc-devs mailing list
> ghc-devs@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
_______________________________________________
ghc-devs mailing list
ghc-devs@haskell.org
http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
