#13731: DeriveFunctor and friends don't understand type families -------------------------------------+------------------------------------- Reporter: spacekitteh | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 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): What would you rather the error message say? I do think the phrase "the type variable" is unfortunate, as it should rather be "the //last// type variable" (since there can be more than one). But other than that, it's pretty spot-on: if you're using the last type variable within another type, it must be a data type, and `ExtensionType` is not a data type. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13731#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler