[GHC] #13604: regression in ghc 8.2.1-rc1 (8.2.0.20170404)

[GHC]

#13604: regression in ghc 8.2.1-rc1 (8.2.0.20170404)
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        Reporter:  George            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHCi              |              Version:  8.2.1-rc1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by ezyang):

 In principle, one ought to be able to pass `-O2` to GHCi to make this
 happen. However, it turns out you also must pass `-fobject-code`, at which
 the desired behavior is seen.

 {{{
 ezyang at sabre:~$ ghc-8.2 -O2 -c A.hs
 ezyang at sabre:~$ ghc-8.2 -O2 -c A.hs -dynamic
 ezyang at sabre:~$ ghc-8.2 --interactive -O2

 when making flags consistent: warning:
     -O conflicts with --interactive; -O ignored.
 GHCi, version 8.2.0.20170413: http://www.haskell.org/ghc/  :? for help
 Prelude> :load A.hs
 [1 of 1] Compiling A                ( A.hs, interpreted ) [flags changed]
 Ok, modules loaded: A.
 *A>
 Leaving GHCi.
 ezyang at sabre:~$ ghc-8.2 --interactive -O2 -fobject-code
 GHCi, version 8.2.0.20170413: http://www.haskell.org/ghc/  :? for help
 Prelude> :load A.hs
 Ok, modules loaded: A (A.o).
 Prelude A>
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13604#comment:9>
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