#9600: Bad error message: Applicative is not a derivable class -------------------------------------+------------------------------------- Reporter: nh2 | Owner: | JohnWiegley Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: Phab:D216 -------------------------------------+------------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"4f80ec0ee438800d95673a4898e69371957fed09/ghc" 4f80ec0e/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="4f80ec0ee438800d95673a4898e69371957fed09" Improve error message for newtypes and deriving clauses Summary: Change the error message generated when a deriving clause related to a newtype fails to always suggested trying GeneralizedNewtypeDeriving, even in situations where it may not work. Fixes #9600. Test Plan: testsuite/deriving/should_fail/9600.hs Reviewers: austin, bgamari, simonpj Rebased-by: bgamari Reviewed By: simonpj Subscribers: bgamari, hvr, simonmar, carter Differential Revision: https://phabricator.haskell.org/D216 GHC Trac Issues: #9600 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9600#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler