We want the warning to be in place for _all_ of the methods added by the `should` syntax.  that includes `unstub`, `stub_chain`, `as_null_object`, `null_object?`, `received_message?` and `any_instance`.

Actually, seeing all these methods makes me think that it would be beneficial if the warning message included the method name in it, so it should pass the method name through to the `warn` method you've defined.  Maybe it could say something like:

``` ruby
RSpec.deprecate("Using :#{method_name} from the old `:should` syntax without explicitly enabling the syntax",
                :replacement => "the new `:expect` syntax or explicitly enable `:should`")
```