False positive with instanceof pattern

[pdolezal]

The instanceof pattern introduced in Java 16 emits code with possibly unnecessary stores. With a code snippets like

if (object instanceof Foo foo) {
    return foo.bar();
}

then the analyzer produces USBR_UNNECESSARY_STORE_BEFORE_RETURN.

[janosvitok]

This is how to reproduce the problem: add the following code to src/samples/java/ex/USBR_Sample.java

   public RuntimeException fpPatternMatching(String num) {
        try {
            int i = Integer.parseInt(num);
        } catch (Exception e) {
            if (e instanceof RuntimeException re) {
                return re; // return typecast exception
	    }
        }
        return null;
    }

Note: This is Java 16 feature, so you have to change build.xml:

		<javac srcdir="${samples.dir}" destdir="${samples.classes.dir}" source="16" target="16" deprecation="${javac.deprecation}" debug="${javac.debug}" includeantruntime="false">