#12814: Should GND infer an instance context when deriving method-free classes? -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #11369, #12810 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): I am sure you understand this better than I do, but what happens in a case involving non-regular recursion (e.g. deriving `Eq` for `data X a = A a | B (X (a, a))`)? I argued for the same approach in the setting of `DeriveAnyClass`, and was disappointed that instead a heuristic was adopted that has no reason to be correct in general, so I think something is a bit "broken" here, in the sense of your last paragraph. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12814#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler