anchor.diff:  
   function_declaration : function_head function_name generic_parameter_clause? function_signature function_body  ;
   function_head : attributes? declaration_specifiers? 'func'  ;
  -function_name : identifier |  Operator  ;
  +function_name : identifier |  operator  ;
   function_signature : parameter_clauses function_result? ;
   function_result : '->' attributes? type  ;
   function_body : code_block  ;
  
positive.code: 
  Block_comment : '/*' (Block_comment|.)*? '*/' -> channel(HIDDEN) ; // nesting allow
  
  Line_comment : '//' .*? '\n' -> channel(HIDDEN) ;
negative.code: balanced_token : '('  balanced_tokens? ')'
   | '[' balanced_tokens? ']'
   | '{' balanced_tokens? '}'
   | identifier | expression | context_sensitive_keyword | literal | operator
  // | Any punctuation except ( ,  ')' , '[' , ']' , { , or }
   ;
  
  