[GHC] #10846: PartialTypeSignatures change implicit CallStack behavior

[GHC]

#10846: PartialTypeSignatures change implicit CallStack behavior
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        Reporter:  nitromaster101    |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by nitromaster101):

 Another version of f2 produces the same incorrect behavior:
 {{{#!hs
 f2 :: (?loc :: CallStack, _) => String
 f2 = show $ map (srcLocStartLine . snd) $ getCallStack ?loc
 }}}
 It's the same idea, but now the wildcard is in the constraints, even when
 it unifies with ().

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10846#comment:2>
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