Would that still work with abstract classes?

I'm afraid the issue is still there in tsc 3.4.5 .

A few ideas when writing another for myself:

• target should be of some extend-able type, so that we can class extends target. (from what I tried, it has to be like new () => {}. currently NewableFunction is not one.)
• it seems difficult to handle more complicated cases: a decorator can do anything

I am using this now (it assumes constructor and instances types are not changed):

type ClassDecorator2 = <C extends new(...args: any[])=>{}>(target: C) => C | void;

I just ran into this. Assuming (I think reasonably) that the builtin ClassDecorator type was accurate, I spent far too long thinking I had a bug in my class decorator, when there was none.

If this remains a low priority to get right, I recommend at least making the builtin type much more permissive for anyone else running into this, since decorators are far more flexible than ClassDecorator's current TFunction | void return type.

Just ran into this again (will be every time when using class decorator). Here's the reproducible case

The workaround from previous comment works as long as there's no static methods in the class being decorated. Curios to know how this can improved.

Also note, that application of class decorators does not generate error, even that the intention is to decorate only subclasses of Serializable.

I believe ClassDecorator should accept an optional argument with the base class that can be decorated.