anchor.diff:  
   variable_declaration_head : attributes? declaration_specifiers? 'var'  ;
   variable_name : identifier  ;
  -getter_setter_block : { getter_clause setter_clause?}  | { setter_clause getter_clause }  ;
  -getter_clause : attributes? get code_block  ;
  -setter_clause : attributes? set setter_name? code_block  ;
  +getter_setter_block : '{' getter_clause setter_clause?'}'  | '{' setter_clause getter_clause '}'  ;
  +getter_clause : attributes? 'get' code_block  ;
  +setter_clause : attributes? 'set' setter_name? code_block  ;
   setter_name : ( identifier )  ;
  -getter_setter_keyword_block : { getter_keyword_clause setter_keyword_clause?} | { setter_keyword_clause getter_keyword_clause }  ;
  -getter_keyword_clause : attributes? get  ;
  -setter_keyword_clause : attributes? set  ;
  -willSet_didSet_block : { willSet_clause didSet_clause?} | { didSet_clause willSet_clause }  ;
  -willSet_clause : attributes? willSet setter_name? code_block  ;
  -didSet_clause : attributes? didSet setter_name? code_block  ;
  +getter_setter_keyword_block : '{' getter_keyword_clause setter_keyword_clause?'}' | '{' setter_keyword_clause getter_keyword_clause '}'  ;
  +getter_keyword_clause : attributes? 'get'  ;
  +setter_keyword_clause : attributes? 'set'  ;
  +willSet_didSet_block : '{' willSet_clause didSet_clause?'}' | '{' didSet_clause willSet_clause '}'  ;
  +willSet_clause : attributes? 'willSet' setter_name? code_block  ;
  +didSet_clause : attributes? 'didSet' setter_name? code_block  ;
   
   // GRAMMAR OF A TYPE ALIAS DECLARATION
   
  
positive.code: 
  // GRAMMAR OF A TYPE IDENTIFIER
  
  type_identifier : type_name generic_argument_clause?  type_name generic_argument_clause?. type_identifier  ;
  type_name : identifier  ;
  
  // GRAMMAR OF A TUPLE TYPE
  
negative.code: // GRAMMAR OF AN ENUMERATION DECLARATION
  
  enum_declaration : attributes? union_style_enum | attributes? raw_value_style_enum  ;
  union_style_enum : enum_name generic_parameter_clause?'{' union_style_enum_members?'}'  ;
  union_style_enum_members : union_style_enum_member union_style_enum_members? ;
  union_style_enum_member : declaration | union_style_enum_case_clause  ;
  union_style_enum_case_clause : attributes? 'case' union_style_enum_case_list  ;
  