#12240: Common Sense for Type Classes -------------------------------------+------------------------------------- Reporter: Mathnerd314 | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Mathnerd314): I discussed the proposal with some people on IRC, and the consensus seems to be that, while nobody besides me thinks that implementing this is particularly useful (or possible), they would not immediately reject an implementation. I have started work on this in https://github.com/Mathnerd314/ghc. I am also planning to solve #11948 "correctly" in the same branch, as outlined in the OutsideIn(X) paper:
... the behavior of the solving algorithm [with respect to dictionary instantiation] remains non-deterministic. This [can be fixed] by refraining from applying DINSTW if a local given could match with the wanted constraint (perhaps after instantiating unification variables)
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12240#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler