#9761: Foldable cannot be derived by GND due to redundant contexts -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: bug | Status: patch Priority: normal | Milestone: Component: Core | Version: 7.9 Libraries | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: GHC | Related Tickets: rejects valid program | Test Case: | Blocking: | Differential Revisions: Phab:D425 | -------------------------------------+------------------------------------- Comment (by Herbert Valerio Riedel <hvr@…>): In [changeset:"0a8e8995fd31dd46fa9bdbc7f65984b51c8c13dc/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="0a8e8995fd31dd46fa9bdbc7f65984b51c8c13dc" Remove redundant contexts from Foldable methods New `Foldable` methods accidentally had `Foldable` contexts, which led to type roles being assigned incorrectly and preventing GND from deriving `Foldable` instances. Removing those fixes #9761. Moreover, this patch takes advantage of this fix by deriving `Foldable` (and `Eq`) for `UniqFM`. Differential Revision: https://phabricator.haskell.org/D425 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9761#comment:6> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler