[ghc-steering-committee] Source plugins (#107), Recommendation: accept

[Christopher Allen]

Dear Committee,

Chris Allen here!

GHC source plugins were proposed by Boldizsár Németh.

The PR discussing the proposal is here:
https://github.com/ghc-proposals/ghc-proposals/pull/107

Rendered at:
https://github.com/nboldi/ghc-proposals/blob/patch-4/proposal-source-plugins.rst

This proposal suggests the extension of the existing tlugin support in
GHC with plugins that are able to access and modify the representation
of the Haskell syntax tree and its environment. This would allow tool
developers to base their tools on GHC plugins.

A version of the proposal is already implemented at:
https://phabricator.haskell.org/D4342

My present main concern would be the issues with recompilation that
the current patch introduces but that seems like a problem with an
implementation rather than the proposal. That's an issue for the GHC
devs themselves to sort out, as I understand it.

It's not obvious to me that the unresolved questions could be answered
with deliberation rather than implementation and exploration. I am far
from an expert on GHC plugins but from what I've been able to read
about them I don't see any blockers in this proposal as-written.

I reached out to a couple of people that have hacked on or around GHC
in the past and it seemed like they were most keen to find out what
problems of theirs this proposal would solve. I didn't see any actual
objections raised.

I recommend we accept this proposal in the current form or with
further elaboration at the author's option. However, my recommendation
here defers to the experience of others on the committee who know more
about the plugins API and the substance of this proposal.

-- 
Chris Allen