I support both adding ExtraCommas (minus constraint tuples) and Joachim's suggestion to modify the warning for duplicate exports. Both of these are useful.

The "cleaner diffs" motivation is more compelling than the CPP argument, in my opinion. I often have to work with Python where it's common practice to include trailing commas in multiline lists, and I miss it in Haskell.

Cheers

Simon

On 1 May 2018 at 03:59, Joachim Breitner <mail@joachim-breitner.de> wrote:

Hi,

Am Montag, den 30.04.2018, 19:20 -0500 schrieb Christopher Allen:
> https://github.com/ghc-proposals/ghc-proposals/pull/87
>
> With the provisos mentioned by Simon starting here in mind:
> https://github.com/ghc-proposals/ghc-proposals/pull/87#issuecomment-385536587

I am not against the proposal, but in the interest of fighting
extension fatigue I’d like to draw your attention to this (which I had
just posted at https://github.com/ghc-proposals/ghc-proposals/pull/87#issuecomment-385581915)

If the motivation is really mainly about subexports lists, then we
could simply tell GHC to accept

module Foo
(
Foo(A),
Foo(B),
)
where

without warning about the duplicate export of `Foo`.

Is this good enough to solve the subexport list problem for CPP users?
(probably yes)

Do we still want ExtraCommas, because it is also useful in lists and
other syntactic constructs?
(probably probably; I could be swayed either way).

Cheers,
Joachim

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

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