为什么在尝试使用内部类中的方法引用来调用超类的受保护方法时，我会得到 BootstrapMethodError？

在Java 8中，给定一个包中的超类和一个包中的子类，谁有一个内部类：SuperaSubbSubInner

// Super.java
package a;

public abstract class Super {
   private long value;
   protected final void setValue(long value) {
      this.value = value;
   }
}

//Sub.java
package b;

public class Sub extends Super {
  public void foo() {
    new SubInner().foo();
  }
  private class SubInner {
    void foo() {
      Optional.of(1L).ifPresent(Sub.this::setValue); // Will throw IllegalAccessError at runtime.
      Optional.of(1L).ifPresent(t -> setValue(t)); // However, lambda works.
      setValue(1L); // also works.
    }
  }
}

我的问题是，为什么在这种情况下方法引用无法正常工作，而普通方法调用可以访问超类方法？setValue

另外，如果我尝试这样做，代码无法编译，并且错误似乎与运行时错误一致：在 中具有受保护的访问权限。Sub.super::setValuesetValuea.Super

Exception in thread "main" java.lang.BootstrapMethodError: java.lang.IllegalAccessError: tried to access method a.Super.setValue(J)V from class b.Sub$SubInner
    at b.Sub$SubInner.foo(Sub.java:14)
    at b.Sub.foo(Sub.java:10)
    at b.Sub.main(Sub.java:22)
Caused by: java.lang.IllegalAccessError: tried to access method a.Super.setValue(J)V from class b.Sub$SubInner
    at java.lang.invoke.MethodHandleNatives.resolve(Native Method)
    at java.lang.invoke.MemberName$Factory.resolve(MemberName.java:975)
    at java.lang.invoke.MemberName$Factory.resolveOrFail(MemberName.java:1000)
    at java.lang.invoke.MethodHandles$Lookup.resolveOrFail(MethodHandles.java:1394)
    at java.lang.invoke.MethodHandles$Lookup.linkMethodHandleConstant(MethodHandles.java:1750)
    at java.lang.invoke.MethodHandleNatives.linkMethodHandleConstant(MethodHandleNatives.java:477)
    ... 3 more