[GHC] #14541: Stg lint failure while building ghc-stage2: compiler/stage2/build/Hoopl/Block.o

[GHC]

#14541: Stg lint failure while building ghc-stage2:
compiler/stage2/build/Hoopl/Block.o
-------------------------------------+-------------------------------------
           Reporter:  duog           |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 With the tree at: https://github.com/duog/ghc/tree/trac-14536
 Which fixes ticket:14536
 With build.mk:
 {{{
 BuildFlavour = validate

 ifneq "$(BuildFlavour)" ""
 include mk/flavours/$(BuildFlavour).mk
 endif

 GhcStage2HcOpts    +=  -dcore-lint -dstg-lint -dcmm-lint
 }}}
 building with:
 {{{
 make compiler/stage2/build/Hoopl/Blocks.o
 }}}

 I get the following Stg lint error (extracts, full dump attached):
 {{{
   <no location info>: warning:
        [in body of lambda with binders ds_s4dH :: a_a3as -> b_a3at,
                                        ds1_s4dI :: MaybeO ex_a3ao a_a3as]
       In some algebraic case alternative, number of arguments doesn't
 match constructor:
       JustO (arity 2)
       [a1_s4dK]
 }}}
 ...
 {{{
   $fFunctorMaybeO_$cfmap
     :: forall ex a b. (a -> b) -> MaybeO ex a -> MaybeO ex b
   [GblId,
    Arity=2,
    Caf=NoCafRefs,
    Str=<L,1*C1(U)><S,1*U>,
    Unf=OtherCon []] =
       [] \r [ds_s4dH ds1_s4dI]
           case ds1_s4dI of {
             JustO a1_s4dK [Occ=Once] ->
                 let {
                   sat_s4dL [Occ=Once] :: b_a3at
                   [LclId] =
                       [ds_s4dH a1_s4dK] \u [] ds_s4dH a1_s4dK;
                 } in  JustO [sat_s4dL];
             NothingO -> $WNothingO;
           };
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14541>
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