#12768: 8.0.2 derives invalid code when class method is constrained by itself -------------------------------------+------------------------------------- Reporter: jophish | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 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 jophish): Yes, as 8.1 suggests, this constraint is redundant. I encountered this in the trifecta library. It can be seen in the `rend` and `restOfLine` member functions of the `DeltaParsing` class here https://hackage.haskell.org/package/trifecta-1.6/docs/src/Text.Trifecta.Comb... (this is fixed in trifecta's HEAD now). I imagine that this can happen when a top level constrained function is moved to be a member of a class. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12768#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler