
#14992: Allow existentials to UNPACK -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider {{{ data T a where MkT :: b -> (b->a) -> T a data Wuggle where MkW :: {-# UNPACK #-} !T Int -> Wuggle }}} Here `MkT` has an existential, but there is really no reason that it can't unpack into the data constructor for `MkW`. But it is currently rejected. Fixing this would require quite a bit of new plumbing. E.g. the existential type variable of the worker and wrapper would differ, which is not true today. But morally it's the Right Thing. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14992 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler