[GHC] #13360: Add a flag to enable inferring HasCallStack constraints

[GHC]

#13360: Add a flag to enable inferring HasCallStack constraints
-------------------------------------+-------------------------------------
        Reporter:  gridaphobe        |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              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:                    |
-------------------------------------+-------------------------------------

Comment (by gridaphobe):

 I think I would want GHC to inject `HasCallStack` into explicit type
 signatures.

 One possibility would be to just always add `HasCallStack` as a top-level
 given, and then silently drop it if it's found to be unused. I know GHC
 already has code to warn about unused constraints, but I don't know how
 awkward it would be to make use of that for this purpose.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13360#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler