Re: [GHC] #12026: Pattern match failure in RnNames.hs

#12026: Pattern match failure in RnNames.hs -------------------------------------+------------------------------------- Reporter: davean | Owner: mpickering Type: bug | Status: patch Priority: highest | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2181 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"53f26f5a45f146e1cc988bbcf76a362c877beaa2/ghc" 53f26f5/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="53f26f5a45f146e1cc988bbcf76a362c877beaa2" Forbid variables to be parents in import lists. In the long discussion on #11432, it was decided that when a type constructor is parsed as a variable ((--.->) is one example) then in order to export the type constructor then the user should be required to use the ExplicitNamespaces keyword. This was implemented in quite an indirect manner in the renamer. It is much more direct to enforce this in the parser at the expense of slighty worse error messages. Further to this, the check in the renamer was actually slightly wrong. If the variable was in scope then no error was raised, this was causing panics, see #12026 for an example. Reviewers: austin, bgamari Subscribers: davean, skvadrik, thomie Differential Revision: https://phabricator.haskell.org/D2181 GHC Trac Issues: #12026 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12026#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler