#11444: 8.0 rc1 panics in applyTypeToArgs -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #13027 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Aha! This is closely linked to #13027; read esp comment:23 on that ticket. In that comment I quote this Note from `CoreUtils` {{{ Note [dataToTag speculation] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Is this OK? f x = let v::Int# = dataToTag# x in ... We say "yes", even though 'x' may not be evaluated. Reasons * dataToTag#'s strictness means that its argument often will be evaluated, but FloatOut makes that temporarily untrue case x of y -> let v = dataToTag# y in ... --> case x of y -> let v = dataToTag# x in ... Note that we look at 'x' instead of 'y' (this is to improve floating in FloatOut). So Lint complains. Moreover, it really *might* improve floating to let the v-binding float out }}} The remark about `FloatOut` is ''exactly'' what is happening here. So if we follow the "alternative path" described in comment:23, that'll fix this ticket too. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11444#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler