#8865: Cannot derive well-kinded instance of form ‘Category ----------------------------------------------+---------------------------- Reporter: adinapoli | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: Resolution: | 7.8.1-rc2 Operating System: MacOS X | Keywords: Type of failure: GHC rejects valid program | Architecture: x86_64 Test Case: | (amd64) Blocking: | Difficulty: Unknown | Blocked By: | Related Tickets: ----------------------------------------------+---------------------------- Comment (by simonpj): Oh, don't worry, I can reproduce it with {{{ {-# LANGUAGE GeneralizedNewtypeDeriving #-} module T8865 where import Control.Category newtype T a b = MkT (Either a b) deriving( Category ) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8865#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler