Javadoc in 9 seems to treat all interfaces with only one method as functional interfaces

[Florian Weimer]

* Daniel Fuchs:

> While playing with JDK 9 javadoc command I noticed that it
> seems to treat all single method interfaces as if they were
> functional interfaces - even though they don't have the
> @FunctionalInterface annotation.

Does it take inheritence into account?  If yes, why is this even a
bug?