Right. I'm not requesting local instances as a whole; rather, just access to the desugared typeclass dictionary types. Basically, adding a Dictionary kind, and a type function from Constraint kinds to Dictionary kinds (local instances could involve adding a type function in the reverse
#9819: Create typesafe method of obtaining dictionary types from class definitions, and constraint objects from dictionary types -------------------------------------+------------------------------------- Reporter: | Owner: spacekitteh | Status: new Type: feature | Milestone: request | Version: Priority: normal | Keywords: Component: Compiler | Architecture: Unknown/Multiple Resolution: | Difficulty: Moderate (less Operating System: | than a day) Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by goldfire): Replying to [comment:9 spacekitteh]: direction). Additionally, a Coercible instance for the class and the dictionary would be useful too.
This seems like it would be fairly straightforward to implement and not
involve much design work; the problems seem to only arise when going from Dictionary -> Constraint. Ah. This makes sense. But, before diving into implementation, we need a clear specification of the feature, preferably on a wiki page. The page should contain motivation and examples of programs that you wish to be accepted. Then, we'll all have a better idea of what we're discussing. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9819#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler