#13370: exprIsBottom inconsistend with strictness analyser -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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): PS: the inconsistency actually appears as lint warnings {{{ No alternatives for a case scrutinee not known to diverge for sure: tcGetDefaultTys6 }}} This happens because `FloatOut` hoist an expression like the RHS of `f` above to top level; and then uses `exprBotStrictness_maybe` to give it a cheap-and-cheerful strictness signature, one that says it diverges. That sig enables GHC to discard case alternatives. But then the final demand- analysis phase, just before CoreTidy, returns a more conservative verdict, after which the lint warnings appear. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13370#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler