On Fri, Sep 23, 2016 at 3:00 PM, Simon Peyton Jones
Interesting. Is this case also an example, or is it a non-feature?
class C t where
type K t :: Type
type T t :: K t -> Type
m :: t -> T t a
Ah, that’s quite different! We should do strongly-connected-component analysis of the associated-type declarations within a single class declaration…. but we don’t currently do that. No difficulty in principle, I think.
You could open a ticket. (Do include a link to this email thread and to #12088)
I’ve opened ticket #12612 https://ghc.haskell.org/trac/ghc/ticket/12612.
Assuming GHC accepted this definition, would the Template Haskell trick (or
whatever replaces it) allow defining instances of C?
--
Dave Menendez