Feasibility of using retrie to refactor for Data.List monomorphisation

[bgamari]

In GHC 9.2 Data.List is changing with the expectation that all imports be qualified (or, at very least, bearing an explicit import list). Specifically, we would need to change all occurrences of declarations defined in Data.List to a module prefixed name (e.g. L.map) and change all imports to qualified imports.

As this will be a somewhat invasive change, it would be great to be able to offer a retrie recipe in the GHC 9.2 migration guide. Is this feasible?

[xich]

I think it depends on how automated you want this to be. If the end user is willing to do a little work themselves, then you could do something like:

for fn in map fold; do
  retrie --adhoc "$fn = L.$fn" --import "import qualified Data.List as L"
done

(it would be faster if we did all the rewrites at once by building something with runScript instead of iterating in bash)

But that will rewrite any instance of map, not just the one from Data.List. It will also leave around any existing imports, which will presumably need deleted.

If you want this it be fully automatic, we'd need to solve #10 first and probably build this into/with haskell-language-server (so we have a source of renamed identifiers) cc @pepeiborra. (And also add import deletion/modification, but that is easy.)

What's your timeline? I think I have a handle on how to tackle #10, but am traveling the first couple weeks of July, so not sure how soon I could have something ready.

[pepeiborra]

/cc @OliverMadine who was also looking at a closer integration of retrie with HLS

[bgamari]

Thanks @xich! This isn't urgent but the sooner it can be done the sooner users migrating to 9.2 can benefit.

[chessai]

Please note that it is actually 9.4 - however, the change is going to be reverted and postponed until at least 9.6, possibly later. If retrie could come to handle this change in the meantime, that would greatly benefit the haskell community at large.

[Kleidukos]

9.4 is about to be released, I think it's a good time to get things going on that front. :)