anchor.diff:  
   // GRAMMAR OF A PARENTHESIZED EXPRESSION
   
  -parenthesized_expression : '('  expression_element_list? ')'  ;
  -expression_element_list : expression_element | expression_element ',' expression_element_list  ;
  +parenthesized_expression : '(' expression_element_list? ')'  ;
  +expression_element_list : expression_element (',' expression_element_list)*  ;
   expression_element : expression | identifier ':' expression  ;
   
   // GRAMMAR OF A WILDCARD EXPRESSION
   
   wildcard_expression : '_'  ;
  +
  +// GRAMMAR OF A POSTFIX EXPRESSION
  +
  +postfix_expression
  + : primary_expression                                             # primary
  + | postfix_expression postfix_operator                            # postfix_operation
  + | postfix_expression parenthesized_expression                    # function_call_expression
  + | postfix_expression parenthesized_expression? closure_expression # function_call_with_closure_expression
  + | postfix_expression '.' 'init'                                  # initializer_expression
  + // TODO: don't allow '_' here in Decimal_literal:
  + | postfix_expression '.' Decimal_literal                         # explicit_member_expression1
  + | postfix_expression '.' identifier generic_argument_clause?     # explicit_member_expression2
  + | postfix_expression '.' 'self'                                  # postfix_self_expression
  + | postfix_expression '.' 'dynamicType'                           # dynamic_type_expression
  + | postfix_expression '[' expression_list ']'                     # subscript_expression
  + | postfix_expression '!'                                         # forced_value_expression
  + | postfix_expression '?'                                         # optional_chaining_expression
  + ;
  +
  +// GRAMMAR OF A FUNCTION CALL EXPRESSION
  +
  +/*
  +function_call_expression
  +  : postfix_expression parenthesized_expression
  +  : postfix_expression parenthesized_expression? trailing_closure
  +  ;
  +  */
  +
  +//trailing_closure : closure_expression  ;
  +
  +//initializer_expression : postfix_expression '.' 'init' ;
  +
  +/*explicit_member_expression
  +  : postfix_expression '.' Decimal_literal // TODO: don't allow '_' here in Decimal_literal
  +  | postfix_expression '.' identifier generic_argument_clause?
  +  ;
  +  */
  +
  +//postfix_self_expression : postfix_expression '.' 'self' ;
  +
  +// GRAMMAR OF A DYNAMIC TYPE EXPRESSION
  +
  +//dynamic_type_expression : postfix_expression '.' 'dynamicType' ;
  +
  +// GRAMMAR OF A SUBSCRIPT EXPRESSION
  +
  +//subscript_expression : postfix_expression '[' expression_list ']' ;
  +
  +// GRAMMAR OF A FORCED_VALUE EXPRESSION
  +
  +//forced_value_expression : postfix_expression '!' ;
  +
  +// GRAMMAR OF AN OPTIONAL_CHAINING EXPRESSION
  +
  +//optional_chaining_expression : postfix_expression '?' ;
   
   // GRAMMAR OF OPERATORS
   
   // split the operators out into the individual tokens as some of those tokens
   // are also referenced individually. For example, type signatures use
   // <...>.
  -operator: '/' | '=' | '\\' | '-' | '+' | '!' | '*' | '%' | '<' | '>' | '&' | '|' | '^' | '!' | '.' ;
  +operator: Operator ;
  +
   
   // WHITESPACE scariness:
   
  
positive.code: 
  // GRAMMAR OF AN INTEGER LITERAL
  
  integer_literal : Binary_literal
   | Octal_literal
   | Decimal_literal
   | Hexadecimal_literal
   ;
  Binary_literal : '0b' Binary_digit Binary_literal_characters? ;
  fragment Binary_digit : [01] ;
  fragment Binary_literal_character : Binary_digit | '_'  ;
  fragment Binary_literal_characters : Binary_literal_character Binary_literal_characters? ;
  Octal_literal : '0o' Octal_digit Octal_literal_characters? ;
  fragment Octal_digit : [0-7] ;
  fragment Octal_literal_character : Octal_digit | '_'  ;
  fragment Octal_literal_characters : Octal_literal_character+ ;
  Decimal_literal : Decimal_digit Decimal_literal_characters? ;
  fragment Decimal_digit : [0-9] ;
  fragment Decimal_digits : Decimal_digit+ ;
  
negative.code: 
  // GRAMMAR OF A VARIABLE DECLARATION
  
  variable_declaration
   : variable_declaration_head pattern_initializer_list
   | variable_declaration_head variable_name type_annotation code_block
   | variable_declaration_head variable_name type_annotation getter_setter_block
   | variable_declaration_head variable_name type_annotation getter_setter_keyword_block
  