Java 9 introduced additional attributes String since and boolean forRemoval to the Deprecated annotation.

However, using these attributes in our code leads to a GWT compilation error:

@Deprecated( since = "2017-11-13" ) // -> [ERROR] Line 383: The attribute since is undefined for the annotation type Deprecated
public void foo() {
  [...]
}

Setting -sourceLevel 17 does not prevent this.

It would be nice if this could be supported at some point. At the very least when support for Java 8 is dropped at some point.