#16140: Cannot create type synonym for quantified constraint without ImpredicativeTypes -------------------------------------+------------------------------------- Reporter: Ashley Yakeley | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 Resolution: | Keywords: | QuantifiedConstraints, | ImpredicativeTypes Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
TypeApplications now require language extensions that they didn't before.
This one is more mysterious to me. * The arguments to a VTA is checked with `checkValidType` (see `TcHsType.tcHsTypeApp`). * `checkValidType` uses `check_type`, not `check_pred_ty`. So how come we end up in `check_pred_ty`? I don't think we want to; e.g. `Eq Int` is a perfectly fine instantiation. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16140#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler