#16008: GHC HEAD type family regression involving invisible arguments -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: highest | Milestone: 8.8.1 Component: Compiler (Type | Version: 8.7 checker) | Keywords: TypeFamilies, Resolution: | TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5435 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ryan Scott <ryan.gl.scott@…>): In [changeset:"3899966e4613ec18f365c28d64e9acc163cc1165/ghc" 3899966e/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="3899966e4613ec18f365c28d64e9acc163cc1165" Fix #16008 with a pinch of addConsistencyConstraints Summary: #16008 happened because we forgot to typecheck nullary associated type family instances in a way that's consistent with the type variables bound by the parent class. Oops. Easily fixed with a use of `checkConsistencyConstraints`. Test Plan: make test TEST=T16008 Reviewers: simonpj, goldfire, bgamari Reviewed By: goldfire Subscribers: rwbarton, carter GHC Trac Issues: #16008 Differential Revision: https://phabricator.haskell.org/D5435 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16008#comment:6> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler