Re: Typechecker plugins: request for review and another workflow question

On 10/11/14 15:58, Austin Seipp wrote:

- 2) I am kind of not a fan of having separate 'plugins for core2core' and 'plugins for typechecking' flags, AKA -ftc-plugin and -fplugin. Ideally I would think all plugins could be uniformly specified by simply saying '-fplugin'. This mostly avoids the need for duplication and a naming convention/slew of flags for each case (which we have to catalog and document). There may be an easy way to make this the case; I haven't looked closely yet (it has been some time since I starred at the plugin code, even though Max wrote it and I helped get it merged!)

FWIW, I originally envisaged reusing the existing plugins machinery, and I don't think there are any great problems in doing so (see https://ghc.haskell.org/trac/ghc/wiki/Plugins/TypeChecker). In fact, I had an early implementation of typechecker plugins that did exactly this. I have been wondering, however, about another possible approach. We could: 1. make the constraint solver changes use a *hook*, instead of the plugins directly, and 2. make it possible for plugins to install/modify hooks at some suitable point in the compilation pipeline. I don't know the hooks machinery very well, but if this is feasible it seems like it would provide more power (plugins could modify any part of GHC for which a hook is available) and avoid having multiple overlapping ways of extending GHC. In the future, I can imagine wanting plugins to hook into other parts of GHC (e.g. error message postprocessing for domain-specific error reporting), and this seems like a good way to achieve that. Adam

On Sun, Nov 9, 2014 at 6:17 PM, Iavor Diatchki wrote:

...

Hello,

I just finished merging HEAD into the branch implementing constraint solver plugins (`wip/tc-plugins`), so things should be fully up to date. For ease of review, I squashed everything into a single commit:

https://github.com/ghc/ghc/commit/31729d092c813edc4ef5682db2ee18b33aea6911

could interested folks (I know of SimonPJ, Richard, and Adam) have a look and let me know if things look reasonable?

On a related note: I know that we are using phabricator for code review, but I don't know how to use it yet, so please let me know if I can do something to make the review easier.

-Iavor

-- Adam Gundry, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/