#11142: Type-level skolem capture leads to core lint error -------------------------------------+------------------------------------- Reporter: goldfire | Owner: bgamari Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler (Type | Version: 7.10.2 checker) | 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 simonpj): Also see this Note in `TcHsType`: {{{ Note [Kind generalisation] ~~~~~~~~~~~~~~~~~~~~~~~~~~ We do kind generalisation only at the outer level of a type signature. For example, consider T :: forall k. k -> * f :: (forall a. T a -> Int) -> Int When kind-checking f's type signature we generalise the kind at the outermost level, thus: f1 :: forall k. (forall (a:k). T k a -> Int) -> Int -- YES! and *not* at the inner forall: f2 :: (forall k. forall (a:k). T k a -> Int) -> Int -- NO! Reason: same as for HM inference on value level declarations, we want to infer the most general type. The f2 type signature would be *less applicable* than f1, because it requires a more polymorphic argument. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11142#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler