Hi, thanks for the summary! Am Dienstag, den 18.12.2018, 22:37 -0500 schrieb Eric Seidel:
1. We could make violations of MINIMAL pragmas errors instead of warnings. This would need its own proposal, but it seems like a good idea to me regardless.
2. We could add a special warning/error for empty Lift instances. This is ad-hoc and kludgy, but easily doable since template-haskell is bundled with ghc.
3. We could provide a ghc-fix tool that automatically fixes this issue (and maybe others!). A number of other languages do this and it seems to work well for them. It also sounds like a very nice application of the ghc-exactprint work that Alan has done.
I think 1. is at odds in GHC – we allow partiality in other places as well (partially initialized records, for example). Disallowing it feels like a too fundamental change to the language for the problem we need to solve here. 3. is a neat idea, but again a very big cannon for a niche problem. If we _had_ ghc-fix, then this might be a good approach, and we can keep this in mind as additional evidence that ghc-fix would be good (GSOC anyone), but let's not wait for that here. 2. is good, I think. We have had plenty of such kludges, e.g. around the Monad refactoring. Cheers, Joachim -- Joachim Breitner mail@joachim-breitner.de http://www.joachim-breitner.de/