Re: [ghc-steering-committee] Please review #496: Nothing {}, Shepherd: Eric

I've been away, but I just wanted to chime in that I'm in support. Richard

On Jun 24, 2022, at 6:29 AM, Simon Peyton Jones wrote:

As I say on the proposal thread, I'm in favour.

I do want John to fix the bug in the text https://github.com/ghc-proposals/ghc-proposals/pull/496#issuecomment-1153303...though.

Simon

On Sun, 12 Jun 2022 at 17:19, Eric Seidel mailto:eric@seidel.io> wrote: Dear Committee,

This proposal notes an inconsistency around record wildcard syntax where the wildcard selector/binder cannot be used with nullary record constructors. In other words

``` data Foo = Foo {}

x = Foo {..} ```

is rejected with the error

Illegal `..' notation for constructor ‘Bar’ The constructor has no labelled fields

John notes that this is unnecessary friction that also causes grief for code generators.

The proposal is to allow the use of record wildcard syntax with nullary constructors. Notably the proposal suggests allowing wildcard syntax with both nullary *records* and nullary positional data constructors, ie both of the following would be allowed.

``` data Foo = Foo {} data Foo = Foo

x = Foo {..} ```

I noted on GitHub that this leaves a small asymmetry[1], but I still recommend accepting the proposal as is.

As usual, please discuss the proposal's merits in this thread, and the technical details on GitHub.

[1]: https://github.com/ghc-proposals/ghc-proposals/pull/496#issuecomment-1153221... https://github.com/ghc-proposals/ghc-proposals/pull/496#issuecomment-1153221...

Eric

On Mon, May 30, 2022, at 09:28, Joachim Breitner wrote:

...

Dear Committee,

Empty records with {} have been proposed by John Ericsson

https://github.com/ghc-proposals/ghc-proposals/pull/496 https://github.com/ghc-proposals/ghc-proposals/pull/496 https://github.com/Ericson2314/ghc-proposals/blob/empty-record-wildcards/pro... https://github.com/Ericson2314/ghc-proposals/blob/empty-record-wildcards/pro...

This seems to be about straightening a corner case, so to say. I suggest Eric as the shepherd.

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, Joachim

-- Joachim Breitner mail@joachim-breitner.de mailto:mail@joachim-breitner.de http://www.joachim-breitner.de/ http://www.joachim-breitner.de/

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