PSA: type checker plugins to be affected by upcoming changes to GHC
ben at well-typed.com
Thu Nov 19 04:45:59 UTC 2020
Iavor and Christiaan are two plugin authors that come to mind.
Ideally the patch would also include some migration documentation in the release notes.
On November 18, 2020 11:20:40 PM EST, Richard Eisenberg <rae at richarde.dev> wrote:
>I'm hard at work on two significant refactorings within GHC's
>constraint solver. The first is at
>https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4149. 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
>https://gitlab.haskell.org/ghc/ghc/-/tree/wip/derived-refactor 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.
>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.
>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
>(https://gitlab.haskell.org/ghc/ghc/-/issues/18965) in the future, but
>it's all for a good cause.
>(I have bcc'd plugin authors that I'm aware of. Just adding this in
>case you're surprised at receiving this email.)
>ghc-devs mailing list
>ghc-devs at haskell.org
Sent from my Android device with K-9 Mail. Please excuse my brevity.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the ghc-devs