[GHC] #10344: Make BranchList simpler

[GHC]

#10344: Make BranchList simpler
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        Reporter:  goldfire          |                   Owner:  goldfire
            Type:  task              |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.11
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Changes (by adamgundry):

 * cc: adamgundry (added)


Comment:

 A `Foldable` instance for `BranchList` might well simplify things, but I
 feel it would be simpler still for `BranchList` to be non-recursive,
 something like

 {{{
 data BranchList a br where
   UnbranchedList :: a   -> BranchList a Unbranched
   BranchedList   :: [a] -> BranchList a Branched
 }}}

 You are welcome to disagree, though. :-)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10344#comment:1>
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