Longstanding behavior of invokespecial in HotSpot is to produce an error if, for an invokespecial (other than <init>) the objectref on the stack is not an instanceof the current class.

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Example (see JDK-8009697):

public class A {
  public void m() { System.out.println("A.m"); }
}

public class Test extends A {
  public static void main(String[] args) {
    new A
    dup
    invokespecial A/<init>()V
    invokespecial A/m()V
  }
}

Exception in thread "main" java.lang.VerifyError: Bad type on operand stack in method

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I cannot find this specified. Possibilities:
- It's specified somewhere (perhaps 4.10, which I don't understand very well?), and there's no bug
- By virtue of being common practice, it should be added to the spec
- HotSpot is being too restrictive, and should change (this is not a bug, JDK-8009697 is)

Related rules in the spec:
- Per 4.9.2, invokespecial must name <init>, or a method in the current class or one of its supers
- Per 6.5-invokespecial, _protected_ methods have a restriction like this outside of their package