#13881: Inexplicable error message when using out-of-scope type variable in pattern type signature -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Poor/confusing | Unknown/Multiple error message | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones <simonpj@…>): In [changeset:"3b0e7555fafe73b157a96ca48d8ddc04ad81b231/ghc" 3b0e7555/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="3b0e7555fafe73b157a96ca48d8ddc04ad81b231" Fix lexically-scoped type variables Trac #13881 showed that our handling of lexically scoped type variables was way off when we bring into scope a name 'y' for a pre-existing type variable 'a', perhaps with an entirely different name. This patch fixes it; see TcHsType Note [Pattern signature binders] }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13881#comment:2> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler