#7401: Can't derive instance for Eq when datatype has no constructor, while it is trivial do do so. ---------------------------------+------------------------------------------ Reporter: jpbernardy | Owner: Type: feature request | Status: infoneeded Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.6.1 Keywords: deriving | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: GHC rejects valid program Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | ---------------------------------+------------------------------------------ Comment(by kosmikus): It's useful for example when you're using such a type as an argument to another datatype, which happens to place an Eq constraint on its argument. However, it seems that this works when standalone deriving is used. That might be a viable workaround if it's somehow difficult to fix. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7401#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler