[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
-------------------------------------+-------------------------------------
        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:                    |
-------------------------------------+-------------------------------------

Comment (by RyanGlScott):

 I suppose this is correct, but it hardly feels intuitive to me. The
 definition of `theFloatDigits`, as written above, doesn't seem ambiguous
 at all, given that we are explicitly applying the type `a` to `undefined`.
 The fact that GHC is emitting a warning at all appears to be byproduct of
 the particular implementation it uses to check for ambiguity.

 That being said, it looks like option 2 would be the most sensible option?
 I can't envision a scenario in which not defaulting types in an ambiguity
 check would make a difference.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11947#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler