[GHC] #11947: GHC mistakenly warns about type defaulting in the presence of -XTypeApplications

[GHC]

#11947: GHC mistakenly warns about type defaulting in the presence of
-XTypeApplications
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        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |             Keywords:
      Resolution:                    |  TypeApplications
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Replying to [comment:5 goldfire]:
 > But you should get no warning with `-XAllowAmbiguousTypes`, as that
 skips the ambiguity check that causes the warning. Or am I mistaken here?

 You do get a warning, it seems:

 {{{
 $ /opt/ghc/8.0.1/bin/runghc -Wall -XAllowAmbiguousTypes TheFloatDigits.hs

 TheFloatDigits.hs:6:19: warning: [-Wtype-defaults]
     • Defaulting the following constraint to type ‘Double’ RealFloat a0
     • In the ambiguity check for ‘theFloatDigits’
       In the type signature:
         theFloatDigits :: forall a. RealFloat a => Int
 (53,24)
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11947#comment:6>
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