#13717: Pattern synonym exhaustiveness checks don't play well with EmptyCase -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1-rc1 Resolution: | Keywords: | PatternSynonyms, | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple error/warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): dfeuer, thanks. Now I see why my example didn't trigger any warnings: the definition of the `T` type itself (i.e., the fact that it was a GADT) was what ruled out the possibility of matching on any of its constructors in `tCharAbsurd`. On the other hand, `Fin` does not have this property, and you're relying on the types of the conlikes in its `COMPLETE` set to rule out the possibility of matching anything. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13717#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler