[GHC] #10845: Incorrect behavior when let binding implicit CallStack object

[GHC]

#10845: Incorrect behavior when let binding implicit CallStack object
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        Reporter:  nitromaster101    |                Owner:  gridaphobe
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10846            |  Differential Rev(s):  Phab:D1422
       Wiki Page:                    |
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Comment (by simonpj):

 (I think you are referring to my second version, post-wrinkle.)  You are
 right.  I was hi-jacking `IPOccOrigin` to do "combine and default to empty
 stack".  But yes, I think we can allow it ''not'' to add a location on its
 own behalf.   If you wanted the current effect of `?loc`, you can always
 get the same effect by using
 {{{
 currentLoc :: ?loc :: Location => Location
 currentLoc = ?loc
 }}}
 We'd better document this carefully though.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10845#comment:15>
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