#6068: Panic in GHCi when using functional dependencies and promoted kinds -------------------------------------+------------------------------------ Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.5 Resolution: | Keywords: PolyKinds Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: GHCi crash | Difficulty: Unknown Test Case: polykinds/T6068 | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by Simon Peyton Jones <simonpj@…>): In [changeset:"dff0e99d37f3529041bb2bb66ffda1ea22af14e0/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="dff0e99d37f3529041bb2bb66ffda1ea22af14e0" Fix a subtle bug in kind-mis-matched equalities (Trac #6068) When we have an equality constraint where the LHS and RHS have ill-matched kinds, it get turned into a CIrredEvCan because a CTyEqCan/CFunEqCan are guaranteed kind-compatible. But that in turn led to a bug because in the constraint c = (a:k1) ~ (b:k2) the kind variables k1 and k2 don't show up in tyVarsOfType c. Why not? Because it looks like (~) k1 (a:k1) (b:k2) Maybe (~) should have two kind arguments? That seemed like too big a change for not (we wait for NoKinds), so this patch fixes the bug for now. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6068#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler