#13957: Allow deriving multiparameter type classes with representationally equal arguments -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: 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 RyanGlScott): This doesn't strike me as a very good idea, for a simple reason: it's quite possible you might also have `instance SIEVE I (->)` in scope, which might behave differently from `instance Sieve Identity (->)`. Allowing this sort of thing would make deriving with MPTCs very unpredictable. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13957#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler