#16281: PatternSynonyms doesn't accept non-prenex quantified functions, doesn't float foralls -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This works under GHC HEAD (8.7.20190115) {{{#!hs {-# Language RankNTypes #-} {-# Language ViewPatterns #-} {-# Language PatternSynonyms #-} newtype Logic a = Logic (forall xx. (a -> (xx -> xx)) -> (xx -> xx)) runLogic :: Logic a -> forall xx. (a -> xx -> xx) -> (xx -> xx) runLogic (Logic logic) = logic pattern L :: (forall xx. (a -> xx -> xx) -> xx -> xx) -> Logic a pattern L f <- (runLogic -> f) }}} I was under the impression that these would be equivalent {{{#!hs runLogic :: Logic a -> forall xx. (a -> xx -> xx) -> (xx -> xx) runLogic :: Logic a -> (a -> xx -> xx) -> (xx -> xx) }}} apart from the order of visible type application and such, but it fails: {{{#!hs {-# Language RankNTypes #-} {-# Language ViewPatterns #-} {-# Language PatternSynonyms #-} newtype Logic a = Logic (forall xx. (a -> (xx -> xx)) -> (xx -> xx)) runLogic :: Logic a -> (a -> xx -> xx) -> (xx -> xx) runLogic (Logic logic) = logic pattern L :: (forall xx. (a -> xx -> xx) -> xx -> xx) -> Logic a pattern L f <- (runLogic -> f) }}} {{{ $ ... -ignore-dot-ghci 1022_bug.hs GHCi, version 8.7.20190115: https://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 1022_bug.hs, interpreted ) 1022_bug.hs:11:29: error: • Couldn't match expected type ‘forall xx. (a -> xx -> xx) -> xx -> xx’ with actual type ‘(a -> xx0 -> xx0) -> xx0 -> xx0’ • In the declaration for pattern synonym ‘L’ • Relevant bindings include f :: (a -> xx0 -> xx0) -> xx0 -> xx0 (bound at 1022_bug.hs:11:29) | 11 | pattern L f <- (runLogic -> f) | ^ Failed, no modules loaded. Prelude> }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16281 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler