[ghc-steering-committee] Proposal #624 on linear let-bindings; recommendation: accept

[Arnaud Spiwack]

Moritz: there's one breakage introduced (but only for users of LinearTypes,
which is considered experimental), namely that LinearTypes is proposed to
now imply MonoLocalBinds.

On Thu, 25 Jan 2024 at 07:18, Moritz Angermann <moritz.angermann at gmail.com>
wrote:

> I'll have to recuse myself from this, as much of this is currently going
> above my head. My overall understanding is that
> this mostly relaxes what we accept, and therefore won't break existing
> code?
>
> Best,
>  Moritz
>
> On Thu, 25 Jan 2024 at 00:39, Arnaud Spiwack <arnaud.spiwack at tweag.io>
> wrote:
>
>> On Wed, 24 Jan 2024 at 16:39, Simon Peyton Jones <
>> simon.peytonjones at gmail.com> wrote:
>>
>>> Do newtypes make a difference?  E.g      let N x = e in ...
>>> where N is the data contructor of a newtype?
>>>
>>
>> I don't think it has too. So for the moment, I vote to stick to the
>> current proposal and consider this like all lazy non-variable patterns:
>> must be unrestricted.
>>
>> I suspect that there's a possible refinement where we say that a happy
>> pattern is either:
>> - A variable
>> - Strict
>> - A newtype constructor where the inner pattern is happy.
>>
>> (then if pat is an unhappy pattern, `let pat` must be unrestricted).
>>
>> But I don't think I'm quite ready to go there for the time being, and
>> that'll be a backward compatible change if we change our mind.
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>

-- 
Arnaud Spiwack
Director, Research at https://moduscreate.com and https://tweag.io.
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