#11475: Lint should check for inexhaustive alternatives -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: 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): Ah yes, that is tricky. I'm really not sure how far it is profitable to go here. That is, when does keeping Lint happy become burdensome? But let me suggest a possible approach for this particular case. * Ids have Unfoldings inside them. One such is `OtherCon [AltCon]` (see `CoreSyn`) which says "this Id does not match any of these constructors". * Since they are Ids even lambda-bound variables may have unfoldings. I'm in two minds about whether this is a good idea, but you could give the `\y` in the defn of `lvl` above a `OtherCon[A,B]` unfolding. Then you wouldn't get a Lint error from the `case` in `lvl`. * But in exchange you'd have a new thing to check: that `lvl` was indeed applied to arguments that were not `A` or `B`. So I'm not sure we are any further forward. Maybe this can only be done with a better flow analysis... a "super-Lint" if you like. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11475#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler