#11509: Incorrect error message in StandaloneDeriving: "The data constructors of <typeclass> are not all in scope" -------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc1 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 simonpj): Ha! Interesting. The error message embodies the assumption that in {{{ instance .. => C (T a b c) }}} that `T` is an algebraic data type; but here is is a class. So a question arises: * Does GND work for classes? Well, does this work? {{{ instance (Typeable a, SC (Serializable a)) => SC (Serializable (MyList a)) where dict = coerce (dict :: Static (Dict (Serializable [a]))) }}} If we got past the test, I think that's what we'd generate. I suspect you'll get a similar error from the `corece`, but try it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11509#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler