[GHC] #12650: Too many warnings about consistentCafInfo (was: Too many warnigns about consistentCafInfo)

[GHC]

#12650: Too many warnings about consistentCafInfo
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               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:                    |
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Description changed by mpickering:

Old description:

> Building GHC with debug on yiedls in many (97!) warnings of the form
> {{{
> WARNING: file compiler/stgSyn/CoreToStg.hs, line 252
>   $fFunctorIOEnv True False
> }}}
>
> The code in question is
> {{{
> -- Assertion helper: this checks that the CafInfo on the Id matches
> -- what CoreToStg has figured out about the binding's SRT.  The
> -- CafInfo will be exact in all cases except when CorePrep has
> -- floated out a binding, in which case it will be approximate.
> consistentCafInfo :: Id -> GenStgBinding Var Id -> Bool
> consistentCafInfo id bind
>   = WARN( not (exact || is_sat_thing) , ppr id <+> ppr id_marked_caffy
> <+> ppr binding_is_caffy )
>     safe
>   where
>     safe  = id_marked_caffy || not binding_is_caffy
>     exact = id_marked_caffy == binding_is_caffy
>     id_marked_caffy  = mayHaveCafRefs (idCafInfo id)
>     binding_is_caffy = topStgBindHasCafRefs bind
>     is_sat_thing = occNameFS (nameOccName (idName id)) == fsLit "sat"
> }}}
>
> It would be nice to have less warnings, to make them more useful. I don’t
> know if the warning is not right, or if there is something that can be
> fixed about the thing it is warning about.

New description:

 Building GHC with debug on yields in many (97!) warnings of the form
 {{{
 WARNING: file compiler/stgSyn/CoreToStg.hs, line 252
   $fFunctorIOEnv True False
 }}}

 The code in question is
 {{{
 -- Assertion helper: this checks that the CafInfo on the Id matches
 -- what CoreToStg has figured out about the binding's SRT.  The
 -- CafInfo will be exact in all cases except when CorePrep has
 -- floated out a binding, in which case it will be approximate.
 consistentCafInfo :: Id -> GenStgBinding Var Id -> Bool
 consistentCafInfo id bind
   = WARN( not (exact || is_sat_thing) , ppr id <+> ppr id_marked_caffy <+>
 ppr binding_is_caffy )
     safe
   where
     safe  = id_marked_caffy || not binding_is_caffy
     exact = id_marked_caffy == binding_is_caffy
     id_marked_caffy  = mayHaveCafRefs (idCafInfo id)
     binding_is_caffy = topStgBindHasCafRefs bind
     is_sat_thing = occNameFS (nameOccName (idName id)) == fsLit "sat"
 }}}

 It would be nice to have less warnings, to make them more useful. I don’t
 know if the warning is not right, or if there is something that can be
 fixed about the thing it is warning about.

--

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12650#comment:4>
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