Re: Specializing functions with implicit parameters

On Mar 14, 2020, at 20:03, Sandy Maguire wrote:

What GHC are you testing against? I suspect https://gitlab.haskell.org/ghc/ghc/merge_requests/668 https://gitlab.haskell.org/ghc/ghc/merge_requests/668 will fix this.

I’ve tested against HEAD. I think the change you link is helpful, but it doesn’t quite get there: the usage gets dumped before specHeader even gets a chance to look at the call. The relevant bit of code is here: https://gitlab.haskell.org/ghc/ghc/blob/1de3ab4a147eeb0b34b24a3c0e91f174e6e5... https://gitlab.haskell.org/ghc/ghc/blob/1de3ab4a147eeb0b34b24a3c0e91f174e6e5... Specifically, this line seals the deal: ClassPred cls _ -> not (isIPClass cls) -- Superclasses can't be IPs So maybe the right fix is just to change the role of type_determines_value so that it turns SpecDicts into UnspecArgs, and then with your change everything would just happily work out.