[GHC] #11179: Allow plugins to access "dead code"

[GHC]

#11179: Allow plugins to access "dead code"
-------------------------------------+-------------------------------------
        Reporter:  lerkok            |                Owner:
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10823            |  Differential Rev(s):  Phab:D3073
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 I'm getting lost here

 * First:
 > It would be nice if plugins could see a "faithful" representation of the
 source code
   I have no idea what that means, but by all means open a new feature
 request with a proposed design.

 * Second: should `simpleOptPgm` be a separate pass?   The reason it's put
 in the back of the desugarer is not adequately documented.   So it'd be
 worth a try if there is some benefit (what is the benefit?).  You'd also
 need to ensure that Lint did not check the output of the desugarer, only
 the output of that first pass.  `simpleOptPgm` really discards a LOT of
 junk sometimes!

 * Third, returning to the original question of the ticket, how can we keep
 all the binders alive in the output of `simpleOptPgm`?  For that I like
 the approach you are taking in Phab:D3073; having a keep-alive set is
 nicer than messing with the guts of the analysis.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11179#comment:18>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler