[GHC] #16192: Simplifier does not preserve dependency ordering of the program

16 Jan 2019

      #16192: Simplifier does not preserve dependency ordering of the program
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           Reporter:  osa1           |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.6.3
           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:
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 I noticed this some time ago, but I thought this is expected, because
 there's a comment in CoreLint that mentions this:

 {{{
 lintCoreBindings dflags pass local_in_scope binds
   = initL dflags flags in_scope_set $
     addLoc TopLevelBindings         $
     lintLetBndrs TopLevel binders   $
         -- Put all the top-level binders in scope at the start
         -- This is because transformation rules can bring something
         -- into use 'unexpectedly'
     ...
 }}}

 However talking to SPJ today he mentioned that in Core we should actually
 preserve dependency ordering, hence this ticket.

 I'll update with a reproducer.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16192
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