anchor.diff:      |   expression ('*' | '/' | '%') expression
       |   expression ('+' | '-') expression
       |   expression ('<' '<' | '>' '>' '>' | '>' '>') expression
  -    |   expression ('<=' | '>=' | '>' | '<') expression
  +    |   expression op=('<=' | '>=' | '>' | '<') expression
       |   expression 'instanceof' typeSpec
       |   expression ('==' | '!=') expression
       |   expression '&' expression
  
positive.code:     ;
  
  resources
      :   resource (';' resource)*
      ;
  
  resource
  
negative.code:     ;
  
  classDeclaration
      :   'class' name=Identifier typeParameters?
          ('extends' typeSpec)?
          ('implements' typeList)?
          classBody
  