#11225: Unable to provide type signature for pattern synonym -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: patsyn/T11224 | Blocked By: Blocking: | Related Tickets: #11224 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ {-# language PatternSynonyms , ViewPatterns #-} import Text.Read pattern PRead a <- (readMaybe -> Just a) }}} GHC infers the type correctly for `PRead` but it is impossible provide a signature. See #11224 for more discussion about why. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11225 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler