**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.

typeCheckPass(PropTypes.instanceOf(String), undefined);
    });
    it('should warn for missing required values', function() {
      typeCheckFail(
        PropTypes.instanceOf(String).isRequired, null, requiredMessage
      );
      typeCheckFail(
        PropTypes.instanceOf(String).isRequired, undefined, requiredMessage
      );
    });
    it('should warn if called manually in development', function() {
      spyOn(console, 'error');
      expectWarningInDevelopment(PropTypes.instanceOf(Date), {});
      expectWarningInDevelopment(PropTypes.instanceOf(Date), new Date());
      expectWarningInDevelopment(PropTypes.instanceOf(Date).isRequired, {});
      expectWarningInDevelopment(PropTypes.instanceOf(Date).isRequired, new Date());
    });
  });
  describe('React Component Types', function() {
    beforeEach(function() {
      MyComponent = React.createClass({
        render: function() {
          return <div />;
        },
      });
    });
    it('should warn for invalid values', function() {
      var failMessage = 'Invalid prop `testProp` supplied to ' +
        '`testComponent`, expected a ReactNode.';
      typeCheckFail(PropTypes.node, true, failMessage);