#11385: Unify named wildcards in different type applications -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.1 checker) | Keywords: Resolution: | NamedWildCards TypeApplications 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 Iceland_jack): Trying to wrap the [https://hackage.haskell.org/package/reflection reflection] API without `Proxy`, is there a way to implement this without visible type abstraction? This is `reflect` {{{#!hs reflect_ :: forall (s :: *) a. Reifies s a => a reflect_ = reflect @s Proxy reify_ :: a -> (forall (s :: *). Reifies s a => r) -> r reify_ a f = reify a (\(Proxy :: Proxy s) -> f @s) }}} Would this allow {{{#!hs reify 10 $ \p -> reflect p + reflect p }}} to be written as `↓`? {{{#!hs reify_ 10 $ \ @p -> reflect_ @p + reflect_ @p }}} ---- Minimal `reflection` API: {{{#!hs {-# Language RankNTypes, TypeApplications, KindSignatures, MultiParamTypeClasses, FunctionalDependencies, ScopedTypeVariables, AllowAmbiguousTypes #-} import Unsafe.Coerce data Proxy k = Proxy class Reifies s a | s -> a where reflect :: proxy s -> a newtype Magic a r = Magic (forall (s :: *). Reifies s a => Proxy s -> r) reify :: forall a r. a -> (forall (s :: *). Reifies s a => Proxy s -> r) -> r reify a k = unsafeCoerce (Magic k :: Magic a r) (const a) Proxy {-# INLINE reify #-} }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11385#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler