#12882: Unexpected constraint when using ExistentialQuantification -------------------------------------+------------------------------------- Reporter: danilo2 | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: invalid | 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 danilo2): rwbarton, mpickering: very interesting, thanks for clarification! By the way, is there any other way to create `Elem`-like newtype, which will just ensure GHC that this constraint would be meet? I dont want to pass the dictionary in runtime. I just want to tell the type system that if I ever created `Elem t`, `t` is Typeable. The reason behind it is that I dont want constraint on `t` to appear on functions processing `Elem t`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12882#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler