**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.

'Required prop `testProp.key` was not specified in `testComponent`.'
      );
    });
    it('should warn for invalid key types', function() {
      typeCheckFail(PropTypes.shape({key: PropTypes.number}),
        {key: 'abc'},
        'Invalid prop `testProp.key` of type `string` supplied to `testComponent`, ' +
        'expected `number`.'
      );
    });
    it('should be implicitly optional and not warn without values', function() {
      typeCheckPass(
        PropTypes.shape(PropTypes.shape({key: PropTypes.number})), null
      );
      typeCheckPass(
        PropTypes.shape(PropTypes.shape({key: PropTypes.number})), undefined
      );
    });
    it('should warn for missing required values', function() {
      typeCheckFail(
        PropTypes.shape({key: PropTypes.number}).isRequired,
        null,
        requiredMessage
      );
      typeCheckFail(
        PropTypes.shape({key: PropTypes.number}).isRequired,
        undefined,
        requiredMessage
      );
    });