[ghc-steering-committee] Defaulting rules

[Simon Peyton Jones]

This usually happens with mail from me via a mailing list, where the mailing list server has failed to do the right thing.  So I think it’s the ghc-steering-committee mail forwarder.

I’ll send an email direct to you, and you can see if it’s flagged the same way.

Simon

From: Simon Marlow [mailto:marlowsd at gmail.com]
Sent: 09 February 2017 08:59
To: Simon Peyton Jones <simonpj at microsoft.com>
Subject: Re: [ghc-steering-committee] Defaulting rules

Hi Simon, email from you is being marked as spam by gmail.  I only just discovered this, and I have several of your messages in my spam folder.  Gmail shows the following diagnostic:

[cid:image001.png at 01D282C2.52B92F60]
​Which suggests that perhaps it's a problem at your end, maybe you could get someone to look into it?

Cheers
Simon


On 3 February 2017 at 17:38, Simon Peyton Jones <simonpj at microsoft.com<mailto:simonpj at microsoft.com>> wrote:
Dear GHC steering committee
Advice needed.

•         Some time ago amindfv submitted https://ghc.haskell.org/trac/ghc/ticket/12923.  He offered a patch 8 weeks ago.

•         There wasn’t much discussion about the proposed change, nor did anyone ask him to undertake the GHC proposals process

•         It’s a small change, but it is a user-facing one

•         The design isn’t obvious to me; see comment:12.

•         We could change it now and change it again later; it’s a corner case

•         It matters to him and his customers.
So, should we let it in?
It’s about the defaulting mechanism.  With an unsolved constraint (C alpha) where alpha is otherwise unconstrained, GHC will try a series of types to fill in alpha.  We extended the rules with ExtendedDefaultRules.  He wants a further extension.
I hate slipping things in late, actually after the deadline; but the fault is partly ours for not proactively warning people with open patches.
Opinions?
Simon

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