Update changelog and cleanup comments

Changelog.md

@@ -1,9 +1,16 @@
-### DEv
+### Dev
 
 Enhancements
 
 * Clean up some internal use of Enumerable methods. (Vipul A M)
 
+Bug fixes
+
+* Refactor memoized helpers (let, subject, named subject) to use an internalised
+  method name to avoid conflict with outside methods. Avoids complex ordering
+  issues with `LetDefinitions` module. See #908 #817 #871 rspec/rspec-rails#738 .
+  (Andy Lindeman, Jon Rowe)
+
 ### 2.14.0.rc1 / 2013-05-27
 [full changelog](http://github.com/rspec/rspec-core/compare/v2.13.1...v2.14.0.rc1)
 

lib/rspec/core/memoized_helpers.rb

@@ -481,14 +481,14 @@ def self.memoized_method_name_for(name, let_or_subject)
 
       # @api private
       def self.define_memoized_method(example_group, name, memoized_method_name, &block)
-        # We have to pass the block directly to `define_method` to
-        # allow it to use method constructs like `super` and `return`.
         raise "#let or #subject called without a block" if block.nil?
 
-        MemoizedHelpers.module_for(example_group).__send__(:define_method, memoized_method_name, &block)
+        # We have to pass the block directly to `define_method` to
+        # allow it to use method constructs like `super` and `return`.
+        module_for(example_group).__send__(:define_method, memoized_method_name, &block)
 
         # Apply the memoization. The method has been defined in an ancestor
-        # module so we can use `super` here to get the value.
+        # module so we can use the decorated name here to get the value.
         example_group.__send__(:define_method, name) do
           __memoized.fetch(name) { |k| __memoized[k] = send(memoized_method_name, &nil) }
         end

spec/rspec/core/memoized_helpers_spec.rb

@@ -620,6 +620,7 @@ def define_and_run_group
     context "when included modules have hooks that define memoized helpers" do
       it "allows memoized helpers to override methods in previously included modules" do
         group = ExampleGroup.describe do
+          # this replicates the ordering scenario that breaks in #817
           include Module.new {
             def self.included(m); m.let(:unrelated) { :unrelated }; end
           }