[GHC] #15737: Implement sconcat Semigroup Instances for Tuples

[GHC]

#15737: Implement sconcat Semigroup Instances for Tuples
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           Reporter:  andrewthad     |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.6.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 For some semigroups, the user-defined `sconcat` performs asymptotically
 better than the default. The semigroup instances for tuples should create
 a list of each component individually, use `sconcat` for the underlying
 type, and then zip the tuples back together.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15737>
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