#11290: T6031: *** Core Lint errors : in result of Common sub-expression *** -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 7.11 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | deriving/should_compile/T6031, | deriving/should_run/T7931 (WAY=hpc) Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Ah. The trouble is that the previous float-out pass transforms {{{ f = ...(case $cshowsPrec_aQi of { })... x{str=bot} = case $cshowsPrec_aQi of { } }}} into {{{ lvl = case $cshowsPrec_aQi of { } f = ...(case $cshowsPrec_aQi of { })... x{str=bot} = case $cshowsPrec_aQi of { } }}} But 'lvl' doesn't have a strictness annotation. Now CSE gets rid of `x` in favour of `lvl`. And then Lint complains when it finds a previously legitimate `(case x of {})`. I have a fix coming, that will deal with this case nicely. It just involves broadening the cases handled by `Note [Bottoming floats]` in `SetLevels`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11290#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler