[GHC] #10846: PartialTypeSignatures change implicit CallStack behavior

[GHC]

#10846: PartialTypeSignatures change implicit CallStack behavior
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              Reporter:              |             Owner:
  nitromaster101                     |
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.2
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 I have two functions, f and f2 which are identical expect for the use of
 PartialTypeSignatures in f2. GHC produces a warning and says that f2's
 wildcard is filled in by String, which is correct.

 {{{#!hs
 {-# LANGUAGE ImplicitParams, PartialTypeSignatures #-}

 import GHC.Types

 f :: (?loc :: CallStack) => String
 f = show $ map (srcLocStartLine . snd) $ getCallStack ?loc

 f2 :: (?loc :: CallStack) => _
 f2 = show $ map (srcLocStartLine . snd) $ getCallStack ?loc

 f_caller = f
 f2_caller = f2
 }}}
 {{{
 [1 of 1] Compiling Main             ( Bug2.hs, interpreted )

 Bug2.hs:8:30: warning:
     Found type wildcard ‘_’ standing for ‘String’
     In the type signature for:
       f2 :: (?loc :: CallStack) => _
 Ok, modules loaded: Main.
 *Main> f_caller
 "[6,11]"
 *Main> f2_caller
 "[9]"
 }}}

 f2_caller should have two entries (f2_caller's line and f2's line), just
 like f_caller.

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