[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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Changes (by dfeuer):

 * status:  upstream => patch
 * differential:   => Phab:D3723


Comment:

 I've submitted Phab:D3723 to remove `bitSize`. My only question is whether
 we should add it back as a function

 {{{#!hs
 bitSize :: FiniteBitSize a => a -> Int
 bitSize = finiteBitSize
 }}}

 to reduce unnecessary breakage. This only goes so far; module import lines
 may need to be changed to fix old code.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12970#comment:7>
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