#12973: No levity-polymorphic arguments -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple LevityPolymorphism | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- As discussed in our [http://cs.brynmawr.edu/~rae/papers/2017/levity/levity.pdf draft paper] on levity polymorphism, you cannot have a levity-polymorphic argument. Here is an example: {{{#!hs {-# LANGUAGE RebindableSyntax, TypeInType, ExplicitForAll #-} module Bug where import qualified Prelude as P import GHC.Exts class Num (a :: TYPE r) where (+) :: a -> a -> a fromInteger :: P.Integer -> a foo :: forall (a :: TYPE r). Num a => a foo = 3 + 4 }}} HEAD panics in `kindPrimRep`, but the code should be rejected. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12973 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler