[GHC] #12096: Attach stacktrace information to SomeException

[GHC]

#12096: Attach stacktrace information to SomeException
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        Reporter:  ndtimofeev        |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Core Libraries    |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by gridaphobe):

 I'm generally in favor of adding `CallStack`s to exceptions (I've often
 cursed myself for using exceptions and having no clue where they were
 thrown).

 I'm not sure this is the best API though. A few thoughts:

 1. I would prefer to not serialize the `CallStack`, i.e. get rid of
 `prettyCallStack`. Clients might want to inspect the `CallStack` when they
 catch an exception.
 2. I wonder if adding the `CallStack` to `SomeException` is the best move.
 If we do this, we're kinda limited to adding the stack to `SomeException`s
 `Show` instance. People (AFAIK) don't usually operate directly on
 `SomeException`, they use `catch` and co. to unwrap the exception, which
 means giving up the `CallStack`. On the other hand, expecting users to add
 `CallStack`s to each exception type is not practical, nor is it clear how
 we'd wire that into `throw`.

 Perhaps (2) can be solved by keeping the `CallStack` in `SomeException`
 and adding a few helper functions, e.g.

 {{{#!haskell
 catchWithCallStack :: Exception e => IO a -> (e -> CallStack -> IO a) ->
 IO a
 }}}

 Thanks for the suggestion!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12096#comment:2>
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