[GHC] #13581: UNPACK should allow recursion that obviously terminates

[GHC]

#13581: UNPACK should allow recursion that obviously terminates
-------------------------------------+-------------------------------------
        Reporter:  ryanreich         |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by ryanreich):

 When you say that it has no idea what `n` is, do you mean that it can't
 figure out if it is `Zero` or not, or that it can't unpack `BigWord n` at
 all simply because `n` is polymorphic?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13581#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler