[ghc-steering-committee] Urgent: exension life cycle proposal

[Simon Marlow]

A few things make this not a straightforward thumbs up for me, though I'm
not strongly against.

What is the interaction with GHC20xx? Presumably we want to say something
like GHC20xx will never include any Deprecated or Legacy extensions? What
about Unsable? if an extension transitions from Stable -> Legacy, would we
remove it from the next GHC20xx?

Something doesn't feel quite right about the warning system. If a module
can start with

{-# OPTIONS_GHC -Wno-XDeprecated #-}
{-# LANGUAGE OverlappingInstances #-}

and silently use an extension that the {build system, user, project} wanted
to disallow, have we achieved anything? Compare this to the current
situation, where the environment can say -XNoOverlappingInstances and code
can override that with {-# LANGUAGE OverlappingInstances #-} - there's
essentially no difference, we just added another layer of disable/override
that isn't buying us anything.

(note I'm viewing this through the spectacles of -Werror, because I've come
to believe that warnings are essentially not useful unless given teeth with
-Werror.)

Cheers
Simon

On Fri, 1 Sept 2023 at 13:18, Vladislav Zavialov <vlad.z.4096 at gmail.com>
wrote:

> I agree that we need a categorisation of extension language flags, but I'm
> not convinced that {Stable, Unstable, Deprecated, Legacy} is the right set
> of labels. In fact, I wouldn't want to commit to any particular
> categorisation before we actually go through all the extensions in GHC and
> see for ourselves that they can be adequately categorized according to the
> proposed system.
>
> The proposal says "classifications of individual language extensions will
> be left to a future proposal". Well, I am skeptical that this separation
> makes sense. I would much prefer if we were discussing a concrete
> categorisation proposal, not just a set of four labels whose implications I
> can't fully grasp.
>
> Vlad
>
> On Fri, Sep 1, 2023 at 11:37 AM Simon Peyton Jones <
> simon.peytonjones at gmail.com> wrote:
>
>> Dear Simon, Vlad, Eric, Chris, Moritz
>>
>> I would love to hear from you about this proposal.  *Please*.
>>
>> I plan to accept it unless I hear dissent.  But I would much rather have
>> an explicit response from you than take silence as assent.  You are a
>> member of the committee, after all!
>>
>> My apologies if I have missed your reply
>>
>> Simon
>>
>
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