#9301: Rank-2 constraints are assigned kind * -------------------------------------+------------------------------------ Reporter: heisenbug | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: duplicate | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by simonpj): The trouble is that I don't know how to do type inference in the presence of polymorphic constraints. It is not a small change. It would be a useful feature. I've wanted it since at least 2000 (see [http://research.microsoft.com/en-us/um/people/simonpj/papers/derive.htm Derivable Type Classes]). Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9301#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler