**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.

});
  describe('Union Types', function() {
    it('should warn but not error for invalid argument', function() {
      spyOn(console, 'error');
      PropTypes.oneOfType(PropTypes.string, PropTypes.number);
      expect(console.error).toHaveBeenCalled();
      expect(console.error.calls.argsFor(0)[0])
        .toContain('Invalid argument supplied to oneOfType, expected an instance of array.');
      typeCheckPass(PropTypes.oneOf(PropTypes.string, PropTypes.number), []);
    });
    it('should warn if none of the types are valid', function() {
      typeCheckFail(
        PropTypes.oneOfType([PropTypes.string, PropTypes.number]),
        [],
        'Invalid prop `testProp` supplied to `testComponent`.'
      );
      var checker = PropTypes.oneOfType([
        PropTypes.shape({a: PropTypes.number.isRequired}),
        PropTypes.shape({b: PropTypes.number.isRequired}),
      ]);
      typeCheckFail(
        checker,
        {c: 1},
        'Invalid prop `testProp` supplied to `testComponent`.'
      );
    });
    it('should not warn if one of the types are valid', function() {
      var checker = PropTypes.oneOfType([
        PropTypes.string,
        PropTypes.number,