<html><head></head><body>Iavor and Christiaan are two plugin authors that come to mind.<br><br>Ideally the patch would also include some migration documentation in the release notes.<br><br>Cheers,<br><br>- Ben <br><br><div class="gmail_quote">On November 18, 2020 11:20:40 PM EST, Richard Eisenberg <rae@richarde.dev> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">Hi all,<br><br>I'm hard at work on two significant refactorings within GHC's constraint solver. The first is at <a href="https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4149.">https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4149.</a> It removes flattening meta-variables and flattening skolems. This is a very nice simplification. Instead, it just reduces type families directly. My other patch (held up by the first) is at <a href="https://gitlab.haskell.org/ghc/ghc/-/tree/wip/derived-refactor">https://gitlab.haskell.org/ghc/ghc/-/tree/wip/derived-refactor</a> and will remove Derived constraints, to be replaced by a little bit of cleverness in suppressing certain confusing error messages. My guess is that either or both of these will invalidate the current behavior of type-checker plugins. Sadly, this is not just a case of finding a new function that replicates the old behavior -- enough is changing under the hood that you might actually have to rewrite chunks of your code.<br><br>I have never written a type-checker plugin, and so I don't currently have advice for you. But if you are a plugin author affected by this change and want help, please reach out -- I would be happy to walk you through the changes, and then hopefully make a little video explaining the process to other plugin authors.<br><br>Neither patch will make it for 9.0, but I expect both to be in 9.2. There may be more where this came from (<a href="https://gitlab.haskell.org/ghc/ghc/-/issues/18965)">https://gitlab.haskell.org/ghc/ghc/-/issues/18965)</a> in the future, but it's all for a good cause.<br><br>(I have bcc'd plugin authors that I'm aware of. Just adding this in case you're surprised at receiving this email.)<br><br>Thanks,<br>Richard<hr>ghc-devs mailing list<br>ghc-devs@haskell.org<br><a href="http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs">http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs</a><br></pre></blockquote></div><br>-- <br>Sent from my Android device with K-9 Mail. Please excuse my brevity.</body></html>