Description Markus Keller 2011-02-25 11:54:52 EST

HEAD

In the code below, the two casts to (List<? extends Number>) in the receiver of the List#get(int) method and in the enhanced for loop are unnecessary, but the compiler doesn't detect this.

package p;
import java.util.ArrayList;
import java.util.List;
class A {
	void x() {
		List<? extends Number> nums = getNums();
		Number num= ((List<? extends Number>) nums).get(0);
		for (Number n : (List<? extends Number>) nums) {
			System.out.println(n);
		}
		
		List<Number> numzzz = new ArrayList<Number>();
		((List<? super Number>) numzzz).set(0, -1);
	}

	private List getNums() {
		return null;
	}
}


While writing this bug, I found bug 158855 and bug 76749, which tell why some casts in the receiver are not completely unnecessary. However, in this case I don't see how class files can be affected.

Note that I do get warnings when I replace all List<? extends Number> with List<Number>, so it looks like the analysis is working fine when the cast only changes type arguments. It just doesn't play wildcards.