Exclude missing marshal_dump and _dump methods from being delegated to
an object's delegation target via the delegate_missing_to extension.
This avoids unintentionally adding instance variables to an object
during marshallization, should the delegation target be a method which
would otherwise add them.

In current versions of Ruby, a bug exists in the way objects are
marshalled, allowing for instance variables to be added or removed
during marshallization (see https://bugs.ruby-lang.org/issues/15968).
This results in a corrupted serialized byte stream, causing an object's
instance variables to "leak" into subsequent serialized objects during
demarshallization.

In Rails, this behavior may be triggered when marshalling an object that
uses the delegate_missing_to extension, if the delegation target is a
method which adds or removes instance variables to an object being
marshalled - when calling Marshal.dump(object), Ruby's built in behavior
will check whether the object responds to :marshal_dump or :_dump, which
in turn triggers the delegation target method in the
responds_to_missing? function defined in
activesupport/lib/active_support/core_ext/module/delegation.rb

While future versions of Ruby will resolve this bug by raising a
RuntimeError, the underlying cause of this error may not be readily
apparent when encountered by Rails developers. By excluding marshal_dump
and _dump from being delegated to an object's target, this commit
eliminates a potential cause of unexpected behavior and/or
RuntimeErrors.

Fixes #36522

Remove extra comments `# Asking for private method` in activesupport/test/core_ext/module_test.rb
Improve docs of using `delegate` with `:private`
Update changelog of #31944

* Add test for the new exception of delegate_missing_to

* Add a changelog entry

* Only check for nil if NoMethodError was raised

* Make method private

* Have to pass both target name and value

* Inline the re-raise

[Rafael Mendonça França + Anton Khamets]

```
/Users/kamipo/src/github.com/rails/rails/activesupport/test/core_ext/module_test.rb:402: warning: `*' interpreted as argument prefix
/Users/kamipo/src/github.com/rails/rails/activesupport/test/core_ext/module_test.rb:420: warning: `*' interpreted as argument prefix
```

This reverts commit 3420a145, reversing
changes made to afb66a5a.

The method is named `delegate_missing_to`, not `delegate_to_missing`

So we shouldn't claim they're there, even when asked explicitly.

See: https://github.com/ruby/ruby/commit/44a2576f798b07139adde2d279e48fdbe71a0148
https://github.com/ruby/ruby/commit/9df88e9cae57aa421230f14500e88f33f127414f

because Struct.new returns a Class, we just can give it a name and use it directly without inheriting from it

Style/SpaceBeforeBlockBraces
Style/SpaceInsideBlockBraces
Style/SpaceInsideHashLiteralBraces

Fix all violations in the repository.

The current code base is not uniform. After some discussion,
we have chosen to go with double quotes by default.

And make sure that it doesn't even try to call the method in the target.

After Ruby 1.9, we can easily get the constants that have been
defined locally by `Module.constants(false)`.

When building decorators, a common pattern may emerge:

    class Partition
      def initialize(first_event)
        @events = [ first_event ]
      end

      def people
        if @events.first.detail.people.any?
          @events.collect { |e| Array(e.detail.people) }.flatten.uniq
        else
          @events.collect(&:creator).uniq
        end
      end

      private
        def respond_to_missing?(name, include_private = false)
          @events.respond_to?(name, include_private)
        end

        def method_missing(method, *args, &block)
          @events.send(method, *args, &block)
        end
    end

With `Module#delegate_missing_to`, the above is condensed to:

    class Partition
      delegate_missing_to :@events

      def initialize(first_event)
        @events = [ first_event ]
      end

      def people
        if @events.first.detail.people.any?
          @events.collect { |e| Array(e.detail.people) }.flatten.uniq
        else
          @events.collect(&:creator).uniq
        end
      end
    end

David suggested it in #23824.

…as discussed #19413

This caused a performance regression since we were decided to do the nil
check in run time not in the load time.

See https://github.com/rails/rails/pull/15187#issuecomment-71760058

Fixes #16956.

sup haters