* lib/ostruct.rb: Move method definitions for getter/setter to be lazy

Patch by @sferik in [GH-1033]: https://github.com/ruby/ruby/pull/1033

Instead of defining two methods -- a reader and writer -- for each
OpenStruct attribute when it is initialized, define them lazily, the
first time either one is called. This adheres to the principle of "pay for
use": methods that are never accessed are never defined. This optimization
makes initialization an order of magnitude faster for objects with 100
attributes. In the worst-case scenario, where every attribute is accessed,
performance is no worse than it is today.

Benchmark
---------
require 'benchmark/ips'
require 'ostruct'

N = 100
ATTRS = (:aa..:zz).take(N)
HASH = Hash[ATTRS.map { |x| [x, x] }]

def ostruct
  OpenStruct.new(HASH)
end

Benchmark.ips do |x|
  x.report('ostruct') { ostruct }
end

-------------------------------------------------
   before       2.279k (± 8.8%) i/s -     11.395k
   after       24.702k (±12.8%) i/s -    122.600k
-------------------------------------------------


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51944 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Sun Sep 27 00:34:31 2015  Zachary Scott  <zzak@ruby-lang.org>
+
+        * lib/ostruct.rb: Move method definitions for getter/setter to be lazy
+          Patch by @sferik in [GH-1033]: https://github.com/ruby/ruby/pull/1033
+
 Fri Sep 25 10:07:25 2015  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
 
 	* lib/net/http.rb: removed unused variable. It's removed at r13648.

lib/ostruct.rb

@@ -90,7 +90,6 @@ class OpenStruct
       hash.each_pair do |k, v|
         k = k.to_sym
         @table[k] = v
-        new_ostruct_member(k)
       end
     end
   end