#8865: Cannot derive well-kinded instance of form ‘Category ----------------------------------------------+---------------------------- Reporter: adinapoli | Owner: Type: bug | Status: closed Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: Resolution: fixed | 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 thoughtpolice): I'm somewhat inclined to think we actually should merge this. At the time the proposal to make `Category` PolyKinded was made, one of the nice parts was that it is essentially an invisible change to already existing code. In some sense I might argue that this is a regression, because while it involves a small 'change' that did not exist prior, it does cause GND over Category to fail in the wild, where it did not before. OTOH, I'm not sure how common the case of using GND to derive Category instances is - this is certainly the first time I've seen it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8865#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler