#13179: Levity-polymorphic data types -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #12708 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Replying to [comment:2 RyanGlScott]:
I'm afraid your definitions may not be what you think they are.
Yes. GHC will do levity polymorphism only upon request, and there is no request in your data constructor types.
If you tried to write truly levity polymorphic definitions for, say, `Product`, it'll actually be rejected!
As well they should be. When creating data constructors, we need to know representations of their fields. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13179#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler