[GHC] #12970: Add default implementation for Bits.bitSize

[GHC]

#12970: Add default implementation for Bits.bitSize
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        Reporter:  txnull            |                Owner:  (none)
            Type:  feature request   |               Status:  upstream
        Priority:  normal            |            Milestone:
       Component:  libraries/base    |              Version:
      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:                    |
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Comment (by ekmett):

 We deprecated bitSize back in 7.8. Removing it outright in 8.4 seems to be
 a reasonably measured move and would preempt the need for this default.
 I'm rather inclined to say we should just finish removing it.

 Either way, we're now past the window in which we should do anyhing either
 way that would affect 8.2.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12970#comment:4>
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