Documentation of QJSValue::isError() contradicts QJSEngine::evaluate()

bool QJSValue::isError() const
Returns true if this QJSValue is an object of the Error class; otherwise returns false.

contradicts

QJSValue QJSEngine::evaluate(const QString & program, const QString & fileName = QString(), int lineNumber = 1)
You can call isError() on the return value to determine whether an exception occurred.

Consider the two snippets:

a) return new Error();

and

b) throw "This is a string";

Judging from the QJSValue's documentation, isError() should return a) true and b) false

Judging from the QJSEngine's documentation, isError() should return a) false and b) true

What's it gonna be? Should isError() really be a wasThrown() ?