Hi. I'm new to this mailing list and have a few questions.

[Vladislav Zavialov]

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) <conversation at 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
> mail at anselmschueler.com
>  
> From: Simon Peyton Jones
> Sent: Tuesday, August 4, 2020 18:44
> To: Richard Eisenberg; "Anselm Schüler (conversations subemail)"
> Cc: ghc-devs at 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-bounces at haskell.org> On Behalf Of Richard Eisenberg
> Sent: 04 August 2020 16:05
> To: "Anselm Schüler (conversations subemail)" <conversation at anselmschueler.com>
> Cc: ghc-devs at 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) <conversation at 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
> mail at anselmschueler.com
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