#14060: TH-reified types can suffer from kind signature oversaturation -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): After re-reading, I'm not sure myself what "if the tycon is applied to any required arguments, then apply their kinds to the tycon's kind before doing further analysis" means. But you've laid out a much better plan of attach than I ever could. Thanks!
If `T` is oversaturated, no annotation is necessary. Otherwise, we can assume `ki0` has the form `forall k1 ... km. s1 -> ... -> sn -> p`.
An injective position in a type `ty` is either `ty` itself, an injective
What happens if we have a dependent quantifier like `forall km -> s1 -> ... -> sn -> p`? Would `km` be included in `K`? My hunch is "yes". position within an injective argument to a tycon, an injective position in a function, or an injective position in the argument to a type variable. The "`ty` itself" bit confuses me. Did you mean "a `ty` itself is in an injective position if `ty` is a tyvar"? I'm guessing you didn't intend for it to be interpreted as "a `ty` itself is always in an injective position", since that would mean that all the variables in `InjTyFam a ... z` would count, where `InjTyFam` is an injective type family.
I do think this is considerably easier than invoking unification.
Certainly. But I know close to nothing about how GHC's unifier works, so this is a pretty low bar for me personally :) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14060#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler