#15412: "Instance head is not headed by a class" when `Constraint` replaced with `type C = Constraint` -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Yes sorry, I should have included the failing code. Here is a version without type families {{{#!hs {-# Language DataKinds, TypeInType, ConstraintKinds #-} import Data.Kind data A :: Type type C = Constraint type UnitC = (() :: C) instance UnitC => Eq A where (==) = undefined }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15412#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler