A type checker plugin for row types

[Nicolas Frisby]

Hello Simon! Thanks for taking a look.

I've attempted to address your Core question by adding a new section to the
wiki page:
https://ghc.haskell.org/trac/ghc/wiki/Plugins/TypeChecker/RowTypes/Coxswain#SomeLightCoreSnorkeling

Regarding the necessary EvTerms, I haven't thought through that enough to
answer. I'll add it to the wiki page.

Thanks. -Nick

On Fri, Sep 15, 2017 at 7:55 AM Simon Peyton Jones <simonpj at microsoft.com>
wrote:

> Nick
>
>
>
> Good work!
>
>
>
> You ask some questions about the constraint solver – I hope that the
> answer from others have helped. If not, do re-ask.
>
>
>
> My main comment is: what does Core look like?  I think your answer is “No
> change to Core, but there are lots of unsafe coerces littered around”.
> But even then I’m not sure.  Even
>
>
>
> f :: Lacks r “f” => V (Row (r .& (“f” .= Int))) -> V (Row (r .& (“f” .=
> Int)))
>
> f n x = ???
>
>
>
> Somehow in the ??? I have to update field n of a tuple x.  How do I do
> that?
>
>
>
> And I’m also very uncomfortable having Core littered with unsafeCoerces.
> I like Core being statically typed.  What is the simplest primitive(s) we
> could add to Core to make it possible to express this stuff type-safely?
>
>
>
> Simon
>
>
>
> *From:* ghc-devs [mailto:ghc-devs-bounces at haskell.org] *On Behalf Of *Nicolas
> Frisby
> *Sent:* 10 September 2017 23:25
> *To:* ghc-devs at haskell.org
> *Cc:* Andres Löh <andres at well-typed.com>; Adam Gundry <adam at well-typed.com>;
> Richard Eisenberg <goldfire at gmail.com>
> *Subject:* A type checker plugin for row types
>
>
>
> Hi all. I've been spending my free time for the last couple months on a
> type checker plugin for row types. The free time waxes and wanes; sending
> an email like this one was my primary goal for the past couple weeks.
>
>
>
> At the very least, I hoped this project would let me finally get some
> hands on experience with OutsideIn. And I definitely have. But I've also
> made more progress than I anticipated, and I think the plugin is starting
> to have legs!
>
>
>
> I haven't uploaded the code yet to github -- it's not quite ready to
> share. But I did do a write up on the dev wiki.
>
>
>
>
> https://ghc.haskell.org/trac/ghc/wiki/Plugins/TypeChecker/RowTypes/Coxswain
>
>
>
> I would really appreciate and questions, comments, and --- boy, oh boy ---
> answers.
>
>
>
> I hope to upload within a week or so, and I'll update that wiki page and
> reply to this email when I do.
>
>
>
> Thanks very much. -Nick
>
>
>
> P.S. -- I've CC'd and BCC'd people who I anticipate would be specifically
> interested in this (e.g. plugins, row types, etc). Please feel free to
> forward to others that come to mind; I know some inboxes abjectly can't
> afford default list traffic.
>
>
>
> P.P.S. -- One hold up for the upload is: which license? I intend to
> release under BSD3, mainly to match GHC since one ideal scenario would
> involve being packaged with/integrated into GHC. But my brief recent
> research suggests that the Apache license might be more conducive to
> eventual widespread adoption. If you'd be willing to advise or even just
> refer me to other write ups, please feel free to email me directly or to
> start a separate thread on a more appropriate distribution list (CC'ing me,
> please). Thanks again.
>
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