GDSL: how to dynamically provide return type for a method invocation

Let's say we have this class:

class Factory {
    Object create(String fullyQualifiedClassName) { /* return an instance of fullyQualifiedClassName */ }
}

Is it possible to write a GDSL that provides the correct return type for an invocation of Factory#create? I think this might be similar to http://youtrack.jetbrains.com/issue/IDEA-81225, which is marked as fixed, but without a mention how it works.