In short, it feels like there ought to be a more general guiding
#15151: Better Interaction Between Specialization and GND -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Research | needed Component: Compiler | Version: 8.4.2 Resolution: | Keywords: deriving 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 andrewthad): principle here to determine whether two instance dictionaries are representationally equivalent. I'm not sure what that would be, though. That seems to sum up the difficulty pretty well. I agree that giving GNDed instances special standing would be bad (and difficult, since that's currently not even tracked). I have no idea what a good way to check instance equality would be. I don't expect that this will be doable in the immediate or even in the far future, but maybe it's a research problem someone may try to tackle one day. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15151#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler