anchor.diff:  // GRAMMAR OF A TUPLE PATTERN
   
   tuple_pattern : '(' tuple_pattern_element_list? ')'  ;
  -tuple_pattern_element_list
  -	:	tuple_pattern_element (',' tuple_pattern_element)*
  -	;
  -tuple_pattern_element : pattern  ;
  +tuple_pattern_element_list :	tuple_pattern_element (',' tuple_pattern_element)* ;
  +tuple_pattern_element : pattern | identifier ':' pattern ;
   
   // GRAMMAR OF AN ENUMERATION CASE PATTERN
   
  -enum_case_pattern : type_identifier? '.' enum_case_name tuple_pattern? ;
  +enum_case_pattern : type_identifier '.' enum_case_name tuple_pattern? ;
   
   // GRAMMAR OF AN OPTIONAL PATTERN
  +
   optional_pattern : identifier_pattern '?' ;
   
   // GRAMMAR OF A TYPE CASTING PATTERN
  
positive.code: 
  // GRAMMAR OF AN EXTENSION DECLARATION
  
  extension_declaration : access_level_modifier? 'extension' type_identifier type_inheritance_clause? extension_body  ;
  extension_body : '{' declarations?'}'  ;
  
  // GRAMMAR OF A SUBSCRIPT DECLARATION
  
  
negative.code:  | protocol_initializer_declaration
   | protocol_subscript_declaration
   | protocol_associated_type_declaration
   | typealias_declaration
   ;
  
  // GRAMMAR OF A PROTOCOL PROPERTY DECLARATION
  