#14395: Redefining pattern synonym in GHCi triggers "‘p’ is untouchable" error -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.2.1 checker) | Keywords: Resolution: | PatternSynonyms 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 simonpj): The error message is indeed confusing, but I think what is happening is this * You load `Bug.hs` * But the interactive context does not have `-XPatternSynonyms` * So when you say {{{ pattern Bar = Nothing }}} GHCi doesn't see `pattern` as a keyword; it sees it as a perfectly ordinary identifier. So its' as if you had written {{{ f Bar = Nothing }}} to define function `f`. * That's why it says, for example {{{ in an equation for ‘pattern’ }}} Quite right! This is a function definition for function `pattern`. It would be cool if it said "Perhaps you meant to use `PatternSynonuyms`" but I don't really see where to put such a test. Anyway I think it's a case of: not a bug, just a confusing error message. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14395#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler