On 26 October 2016 at 11:43, Simon Peyton Jones
As far as I understand it:
· You are plucking a type from the midst of a syntax tree, and displaying it.
· That type might well mention type variables that are bound “further out”
o either by a forall (if this is a sub-tree of a type)
o or by a big lambda
· There are some tricky UI issues in how to display such types to the user.
Right.
Generally, I think it’s mainly up to you to track which type variables are in scope from “further out”. It’s not a property that is stable under transformation, so it’s not part of the TyVar.
Fair enough. That's useful to know, thanks. In that case I can explore alternative approaches.
The typechecker itself uses “tidying” to avoid accidentally displaying distinct type variables in the same way. See TyCoRep.tidyType and related functions. They may be useful to you too.
Ah, the TidyEnv makes sense to me. I think that'll come in handy to review the code to make sure I don't miss anything.
Hard for me to say more… I’m swamped, and there are genuine UI issues here. Maybe some folk on Haskell Café might be interested.
Thanks! I've also got low bandwidth for this, I just posted it to have it out there, as it probably requires some brewing before anything will be implemented anyway.