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

[GHC]

#12970: Add default implementation for Bits.bitSize
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        Reporter:  txnull            |                Owner:  dfeuer
            Type:  feature request   |               Status:  patch
        Priority:  high              |            Milestone:  8.4.1
       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):  Phab:D3723
       Wiki Page:                    |
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Comment (by hvr):

 Replying to [comment:7 dfeuer]:
 > I've submitted Phab:D3723 to remove `bitSize`. My only question is
 whether we should add it back as a function

 to be fair, bitSize was deprecated 3 years ago in GHC 7.8; and when GHC
 8.4 is released that'll be 4 years. If the point of a deprecation is to
 eventually rid the API of the deprecated entity, 4 years (or a 4 rls
 window) is IMO more than enough time for everyone to adapt... ;-)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12970#comment:8>
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