[GHC] #8892: Ghc panics (variable not found)

[GHC]

#8892: Ghc panics (variable not found)
---------------------------------------+-----------------------------------
        Reporter:  jwlato              |            Owner:
            Type:  bug                 |           Status:  new
        Priority:  normal              |        Milestone:
       Component:  Compiler            |          Version:  7.8.1-rc2
      Resolution:                      |         Keywords:
Operating System:  Unknown/Multiple    |     Architecture:
 Type of failure:  Compile-time crash  |  Unknown/Multiple
       Test Case:                      |       Difficulty:  Unknown
        Blocking:                      |       Blocked By:
                                       |  Related Tickets:
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Comment (by jwlato):

 Thanks Simon, with `-dcore-lint` I see *many* warnings like `INLINE binder
 is (non-rule) loop breaker:`, but they seem so common (and some are
 clearly unrelated) that I don't think it's relevant.  In the module that
 errors, I see only this:

 {{{
 *** Core Lint errors : in result of Simplifier ***
 <no location info>: Warning:
     [in body of letrec with binders a125_ajLr3 :: GHC.Prim.State#
 (Control.Monad.Primitive.PrimState
                                                        (GHC.ST.ST
 s2_ajLm9))
                                                   -> (# GHC.Prim.State#
 (Control.Monad.Primitive.PrimState
                                                              (GHC.ST.ST
 s2_ajLm9)),
                                                         () #)]
     foldlM'_loop_ajLpg
       :: Data.Vector.Fusion.Stream.Monadic.SPEC
          -> GHC.Types.Int
          -> GHC.Types.Int
          -> GHC.ST.ST s2_ajLm9 GHC.Types.Int
     [LclId, Arity=4, Str=DmdType] is out of scope
 <no location info>: Warning:
     [in body of letrec with binders a125_ajLr3 :: GHC.Prim.State#
 (Control.Monad.Primitive.PrimState
                                                        (GHC.ST.ST
 s2_ajLm9))
                                                   -> (# GHC.Prim.State#
 (Control.Monad.Primitive.PrimState
                                                              (GHC.ST.ST
 s2_ajLm9)),
                                                         () #)]
     foldlM'_loop_ajLpg
       :: Data.Vector.Fusion.Stream.Monadic.SPEC
          -> GHC.Types.Int
          -> GHC.Types.Int
          -> GHC.ST.ST s2_ajLm9 GHC.Types.Int
     [LclId, Arity=4, Str=DmdType] is out of scope
 }}}

 followed by the simplifier output.  And indeed, there is a `case
 foldlM'_loop_ajLpg something of`, but no binding for
 `foldlM'_loop_ajLpg6`.  At least I've found the offending function now, so
 I may be able to isolate a test case.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8892#comment:2>
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