anchor.diff:          | {has_ver1=true;} ver1=attr_expression_ver1
           | {has_ver2=true;} ver2=attr_expression_ver2
           | {has_cond=true;} cond=attr_expression_cond
  +        | {has_vercond=true;} vercond=attr_expression_vercond
           | attr_expression_default
           | anyattribute
           )*
  
positive.code:     :   { tagMode && !attrMode }?=> 'cond'
      ;
  
  NAME_DEFAULT
      :   { tagMode && !attrMode }?=> 'default'
      ;
  
negative.code:     boolean has_ver1 = false;
      boolean has_ver2 = false;
      boolean has_cond = false;
      boolean has_vercond = false;
  }
      :   TAG_START_ADD
          ( name=attr_variable_name
  