#12540: RFC: Allow not quantifying every top-level quantifiee -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: #14245 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): It's not surprising at all, if you look at it from a certain perspective. After all, in this function: {{{#!hs f :: (forall a. Proxy b -> a -> a) -> Int -> Int f g x = g Proxy x }}} Despite the fact that there's a `forall` in front of `Proxy b -> a -> a`, GHC doesn't complain that `b` is out of scope. That's because the `forall `-or-nothing rule only applies to `forall`s at the top level, which `forall a. Proxy b -> a -> a` is not. That's why `const_ :: (forall a. a -> b -> a)` is accepted, since the `forall` is similarly not at the top level. It's also why this variation is accepted: {{{#!hs const__ :: () => forall a. a -> b -> a const__ = const }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12540#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler