**Do you want to request a _feature_ or report a _bug_?**
Enhancement

**What is the current behavior?**
Element type checker is not as informative as the other ones.

**What is the expected behavior?**
It would be nice to provide the actual type of the prop passed similarly to other type checkers. I.e., instead of 

> Invalid prop `Prop` supplied to `Component`, expected a single ReactElement.

say

> Invalid prop `Prop` of type `type` supplied to `Component`, expected a single ReactElement.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
Seeing this on 15.2.1 but I think it's also applicable to previous versions.

I know the general intention is to move away from prop types, but if there isn't a specific reason for the current behavior I can look into making this more pretty.

expect(console.error.calls.count()).toBe(1);
      expect(
        console.error.calls.argsFor(0)[0].replace(/\(at .+?:\d+\)/g, '(at **)')
      ).toBe(
        'Warning: Failed prop type: num must be 5!\n' +
        '    in Component (at **)'
      );
    });
    it('should not warn if the validator returned null',
      function() {
        spyOn(console, 'error');
        var spy = jasmine.createSpy().and.callFake(
          function(props, propName, componentName) {
            return null;
          }
        );
        Component = React.createClass({
          propTypes: {num: spy},
          render: function() {
            return <div />;
          },
        });
        var instance = <Component num={5} />;
        instance = ReactTestUtils.renderIntoDocument(instance);
        expect(console.error.calls.count()).toBe(0);
      }
    );
  });
});