Headerdoc, Objective-C, anonymous type, ERROR

Question

I have to generate a doc for Xcode's project Objective-C. I have an error anonymous type. I think headerdoc doesn't like @interface section. Can someone resolve that?

My apologies for some grammar mistakes, I have a Xcode's project Objective-C, I want generate a doc with a script (I'm not at my work so I will try explain the problem). In my project I have a class x

.h

/*! headerdoc comment */
@interface x: NSObject
@end

.m

#import x.h
@interface x(){
  /*! headerdoc comment */
  NSString *_xID;
}
@end

@implementation x
/*! headerdoc comment */
-(void)aMethod{
}
@end

And when I run, I have an error "anonymous type", and when I removed @interface section in .m it's working.