1. override
bool debugAssertIsValid()

In checked mode, throws an exception if the object is not in a valid configuration. Otherwise, returns true.

This is intended to be used as follows:

  assert(myDecoration.debugAssertIsValid());

Source

@override
bool debugAssertIsValid() {
  assert(shape != BoxShape.circle ||
         borderRadius == null); // Can't have a border radius if you're a circle.
  return super.debugAssertIsValid();
}