Who holds Java up as a poster child for advanced type systems? You've mad an unintentional straw man argument.

In this particular case, you're using an Integer where a subclass of Enum is called for. The value you're passing may very well be a valid value for the Enum you're trying to use. You may be doing something silly, or it's possible that this is an artifact of generics being bolted on to Java after the fact. In this case, it may be possible for the compiler to infer which Enum you really wanted and insert a runtime check and cast, but then it would be doing you a disservice by silently inserting an opportunity for a runtime error.

I'm not advocating Java's type system, but be glad Java at least has typesafe enums. Every couple of years (across several employers) I run into a very bad bug due to two different return code enums happening to use either 0 or 1 as their "ok" values, and enums of one type being silently cast to the other, resulting in silently okay behavior in the common case and spectacularly bad error recovery in corner cases. Just today I fixed an error where someone had designed an API where an enum of one type was passed to a function needing an enum of a different type, without any translation. Some users had gotten correct behavior by passing an enum of the incorrect type to the API, and some users had followed the API documentation and gotten wrong behavior.

Java's type system is hardly advanced; in fact it's quite primitive.

You have an Integer where it expects a Set.