Fix constantize edge case involving prepend, autoloading and name conflicts

In the following situation:

```ruby
class Bar
end

module Baz
end

class Foo
  prepend Baz
end

class Foo::Bar
end
```

Running `Inflector.constantize('Foo::Bar')` would blow up with a NameError.

What is happening is that `constatize` was written before the introduction
of prepend, and wrongly assume that `klass.ancestors.first == klass`.

So it uses `klass.ancestors.inject` without arguments, as a result
a prepended module is used in place of the actual class.

1 files changed, 1 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index ef3df1240d..fa063af3f4 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -274,7 +274,7 @@ module ActiveSupport
 
           # Go down the ancestors to check if it is owned directly. The check
           # stops when we reach Object or the end of ancestors tree.
-          constant = constant.ancestors.inject do |const, ancestor|
+          constant = constant.ancestors.inject(constant) do |const, ancestor|
             break const    if ancestor == Object
             break ancestor if ancestor.const_defined?(name, false)
             const