#10177: Typeable solver regression -------------------------------------+------------------------------------- Reporter: glguy | Owner: Type: bug | Status: new Priority: highest | Milestone: 7.10.1 Component: Compiler | Version: 7.10.1-rc3 (Type checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: GHC rejects Architecture: | valid program Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- This bug is known and fixed in master. Simon and Austin and Iavor are all aware of it. This ticket exists to ensure that the fix doesn't get lost. This code breaks under the Typeable solver in 7.10.1-rc3 and is fixed in master. The relevant commit in master is 3a0019e3672097761e7ce09c811018f774febfd2 : Improve `Typeable` solver. {{{ {-# LANGUAGE PolyKinds #-} {-# LANGUAGE FlexibleContexts #-} module Bug where import Data.Typeable newtype V n a = V [a] class Typeable a => C a instance (Typeable (V n), Typeable a) => C (V n a) -- Bug.hs:13:10: -- Could not deduce (Typeable (V n a)) -- arising from the superclasses of an instance declaration -- from the context (Typeable (V n), Typeable a) -- bound by the instance declaration at Bug.hs:13:10-50 -- In the instance declaration for ‘C (V n a)’ }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10177 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler