API call to associate Merge Request discussions to their diff

For a given Merge Request, is there an API call that will tie together the discussion to the code diff that is being discussed?

I can all details of a get the discussions for a Merge Request with either of these API calls:
GET /projects/:id/merge_requests/:merge_request_iid/discussions
GET /projects/:id/merge_requests/:merge_request_iid/discussions/:discussion_id

But the JSON response for those does not tell you which chunk of code (the diff) the discussion is referring to or associated with.