This DeprecatedConstantProxy transforms constant to deprecated constant.

OLD_CONST = ActiveSupport::Deprecation::DeprecatedConstantProxy.new('OLD_CONST', 'NEW_CONST')
OLD_CONST = ActiveSupport::Deprecation::DeprecatedConstantProxy.new('OLD_CONST', 'NEW_CONST', deprecator_instance)

When someone use old constant this will trigger warn method on deprecator_instance.

Default deprecator is ActiveSupport::Deprecation.

Methods
C
N
Class Public methods
new(old_const, new_const, deprecator = ActiveSupport::Deprecation.instance)

Source: show | on GitHub 

# File activesupport/lib/active_support/deprecation/proxy_wrappers.rb, line 106
def initialize(old_const, new_const, deprecator = ActiveSupport::Deprecation.instance)
  @old_const = old_const
  @new_const = new_const
  @deprecator = deprecator
end
Instance Public methods
class()

Source: show | on GitHub 

# File activesupport/lib/active_support/deprecation/proxy_wrappers.rb, line 112
def class
  target.class
end