function partial(renderNode, env, scope, path) {
  var template = env.partials[path];
  return template.render(scope.self, env, {}).fragment;
}
Host Hook: partial

  @param {RenderNode} renderNode
  @param {Environment} env
  @param {Scope} scope
  @param {String} path

  Corresponds to:

  ```hbs
  {{partial "location"}}
  ```

  This host hook is invoked by the default implementation of
  the `inline` hook. This makes `partial` a keyword in an
  HTMLBars environment using the default `inline` host hook.

  It is implemented as a host hook so that it can retrieve
  the named partial out of the `Environment`. Helpers, in
  contrast, only have access to the values passed in to them,
  and not to the ambient lexical environment.

  The host hook should invoke the referenced partial with
  the ambient `self`.