Do you want to request a feature or report a bug?
bug

What is the current behavior?
neither the $compile() or subsequent $digest() calls will throw an exception when using a directive with an unsatisfied "require" requirement. NOTE: This is a change from 1.5.10 to 1.6.x

Plunkr: http://plnkr.co/edit/YaJbS1?p=preview

What is the expected behavior?
I expect it to throw when something that's required is not present

What is the motivation / use case for changing the behavior?
It used to work that way and the directive documentation says that $compile with throw (though it takes an extra digest to throw when you use a templateUrl - also doesn't throw if you don't have a 'link' method)

Which versions of Angular, and which browser / OS are affected by this issue? Did this work in previous versions of Angular? Please also test with the latest stable and snapshot (https://code.angularjs.org/snapshot/) versions.
All Versions 1.6.x

Other information (e.g. stacktraces, related issues, suggestions how to fix)
In my plunker, you can copy the context of "index-161.html" to "index.html" to test 1.6.1, and "index-1510.html" to test 1.5.10