[GHC] #9718: Avoid TidyPgm predicting what CorePrep will do

[GHC]

#9718: Avoid TidyPgm predicting what CorePrep will do
-------------------------------------+-------------------------------------
        Reporter:  simonpj           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.8.3
      Resolution:                    |             Keywords:  CodeGen, CAFs
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 When we fix this, let's revisit the patch in comment:36 of #15038. It
 implements a very special case for one error-id, solely because that
 error-id is introduced after the CAF computation has been done in
 !TidyCore.  When we fix this ticket, #9718, we can remove the special case
 and treat all error-ids uniformly.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9718#comment:10>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler