为什么IntelliJ告诉我们从Object到String的转换是多余的？

public class Utils {
    
    private static Map<Class, Function<Object, ?>> functions = new HashMap<>();
    
    static {
        functions.put(String.class, v -> (String) v);
        functions.put(Foo.class, v -> {
            Foo foo = new Foo();
            foo.setA((String) ((Map<String, Object>) v).get("A"));
            foo.setB((String) ((Map<String, Object>) v).get("B"));
            return foo;
        });
    }
}