#15532: Relaxing Levity-Polymorphic Binder Check for Lifted vs Unlifted pointers -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: | LevityPolymorphism Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: 14917 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by andrewthad): We can get a crash if we instead write `example` as: {{{ example :: (a -> Bool) -> (a -> a) -> (a -> b) -> (a -> b) -> a -> b example p k f g a = if p a then f (k (k a)) else g (k a) }}} This fails at runtime with: {{{ internal error: MUT_ARR_PTRS_FROZEN0 object entered! }}} Thanks for helping me see what I was missing. So GHC couldn't possibly generate code for the definition I gave for the levity-polymorphic `map` function given in the original issue. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15532#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler