[GHC] #9049: Expose srcLoc from the assertion architecture to allow better error messages

[GHC]

#9049: Expose srcLoc from the assertion architecture to allow better error
messages
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        Reporter:  nh2               |                   Owner:  gridaphobe
            Type:  feature request   |                  Status:  patch
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.8.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:  Phab:D578
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Comment (by simonpj):

 Re "the second bullet point under Implementation Details", I now
 understand.  Good point.  The issue is this:
 {{{
 f :: (?loc :: CallStack) => IO ()
 f = print (?location :: CallStack)
 }}}
 There are two alternatives for what to pass to `print`:
   * Pass the call site of `print`, pushed onto the passed-in call stack
   * Pass a singleton stack, just the call site of `print`, reflecting the
 change in name.
 You have implemented the first, but I think the latter would perhaps be
 more intuitive.  Does anyone else have opinions?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9049#comment:26>
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