#10180: Lint check: Empty alternatives imply bottoming scrutinee -------------------------------------+------------------------------------- Reporter: nomeata | Owner: nomeata Type: task | Status: infoneeded Priority: normal | Milestone: Component: Compiler | Version: 7.11 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by simonpj):
Simon, what would you prefer: Should `exprIsBottom e` hold for all `e` where the type is a data type with no constructors, or should the lint check take that into account?
Very interesting. * What program gives rise to `case (x::Void) of {}`? * Yes, I think there is a case for making `exprIsBottom` hold for data types with no constructors; after all, such an expression is bound to diverge. * A slightly less pervasive change would to to say that an empty `case` is ok on a data type that has an empty set of constructors. Less pervasive in the sense that it affects this Lint check only, whereas the `exprIsBottom` fix would have broader implications: good ones, I think, but also rare. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10180#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler