Sometimes invalid inner class reference left in .class files produced for interfaces

Compile this:

interface X {
  public String compute();
}

Upon javap'ing the result we see this InnerClass attribute:

public interface X
  SourceFile: "X.groovy"
  InnerClass: 
   #10= #9 of #2; //"1"=class X$1 of class X
  minor version: 0
  major version: 47
  Constant pool:

to X$1. But there is no X$1 produced on disk. Some environments (e.g. eclipse) are attempting to make sense of this and failing with a 'cant find type' message as they can't find the class file. groovy shouldn't be including these references. I believe a decision is made up front that one of these types will be created and then later a decision is taken that there is no need to produce one, but the original reference is left in the interface type (and so it is captured in the attribute).

I changed two things to fix this:

1. Added a method to ClassNode so that it could be told to forget about an interface like this:

    public void forgetInnerClass(InnerClassNode icn) {
        if (innerClasses!=null) {
        innerClasses.remove(icn);
        }
    }

2. And then in the code that decides it doesn't need one (in AsmClassGenerator), forget is called so that the InnerClass attribute isn't added for it:

protected void createInterfaceSyntheticStaticFields() {
    if (referencedClasses.isEmpty()) {
        controller.getClassNode().forgetInnerClass(controller.getInterfaceClassLoadingClass()); // my new line
        return;
    }
    ...

this appears to fix it and continues to pass all the groovy tests.