#10586: GHC 7.10.1 panic due to wildcard in data family instance -------------------------------------+------------------------------------- Reporter: WrenThornton | Owner: thomasw Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #3699 | Differential Revisions: Phab:D1092 -------------------------------------+------------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"d9d2102ea7f6da1bc3a69fa469b89ea843cb8b02/ghc" d9d2102e/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="d9d2102ea7f6da1bc3a69fa469b89ea843cb8b02" Support wild cards in data/type family instances Handle anonymous wild cards in type or data family instance declarations like unnamed type variables. For instance (pun intented): type family F (a :: *) (b :: *) :: * type instance F Int _ = Int Is now the same as: type family F (a :: *) (b :: *) :: * type instance F Int x = Int Note that unlike wild cards in partial type signatures, no errors (or warnings with -XPartialTypeSignatures) are generated for these wild cards, as there is nothing interesting to report to the user, i.e. the inferred kind. Only anonymous wild cards are supported here, named and extra-constraints wild card are not. Test Plan: pass new tests Reviewers: goldfire, austin, simonpj, bgamari Reviewed By: simonpj, bgamari Subscribers: goldfire, thomie Differential Revision: https://phabricator.haskell.org/D1092 GHC Trac Issues: #3699, #10586 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10586#comment:13> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler