[GHC] #14254: The Binary instance for TypeRep smells a bit expensive

[GHC]

#14254: The Binary instance for TypeRep smells a bit expensive
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           Reporter:  dfeuer         |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
           Keywords:  Typeable       |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  performance bug
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 In particular, `get` uses `getSomeTypeRep`. `getSomeTypeRep`, in turn,
 calls `typeRepKind` through its recursion. But `typeRepKind` is itself
 recursive, fully inspecting the spine of its argument. That smells
 quadratic to me. The solution, I believe, is to change the type of
 `getSomeTypeRep` to `BinHandle -> IO (SomeTypeRep, TypeRep Type)`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14254>
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