[GHC] #13187: Strange debug output printed: isPredTy Const Int (, ) Bool Char

[GHC]

#13187: Strange debug output printed: isPredTy Const Int (,) Bool Char
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by goldfire):

 Yes, this use of `pprTrace` is poor. It should be changed to `WARNING`.

 I don't think it indicates a bug, though. The problem is that `Const` is
 over-saturated, in that it looks like it should take only two arguments
 but is given four. In this case, though, the over-saturation is just fine,
 as `Const` is polymorphic in its return kind, specialized to an arrow
 kind.

 It's conceivable that `isPredTy` will get it wrong, in this over-saturated
 case. But I don't see how to do better without zonking, etc., and so I
 vote to punt. It's only about pretty-printing anyway. If someone
 complains, we can re-examine.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13187#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler