[over.sub] - C++20 → C++23

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@@ -1,32 +1,35 @@
 ### Subscripting <a id="over.sub">[[over.sub]]</a>
-A *subscripting operator function* is a function named `operator[]` that
-is a non-static member function with exactly one parameter. For an
-expression of the form
 ``` bnf
-postfix-expression '[' expr-or-braced-init-list ']'
 ```
 the operator function is selected by overload resolution
 [[over.match.oper]]. If a member function is selected, the expression is
 interpreted as
 ``` bnf
-postfix-expression . operator '['']' '(' expr-or-braced-init-list ')'
 ```
 [*Example 1*:
 ``` cpp
 struct X {
   Z operator[](std::initializer_list<int>);
 };
 X x;
-x[{1,2,3}] = 7;                 // OK: meaning x.operator[]({1,2,3\)}
 int a[10];
 a[{1,2,3}] = 7;                 // error: built-in subscript operator
 ```
 — *end example*]

 ### Subscripting <a id="over.sub">[[over.sub]]</a>
+A *subscripting operator function* is a member function named
+`operator[]` with an arbitrary number of parameters. It may have default
+arguments. For an expression of the form
 ``` bnf
+postfix-expression '[' expression-listₒₚₜ ']'
 ```
 the operator function is selected by overload resolution
 [[over.match.oper]]. If a member function is selected, the expression is
 interpreted as
 ``` bnf
+postfix-expression . operator '['']' '(' expression-listₒₚₜ ')'
 ```
 [*Example 1*:
 ``` cpp
 struct X {
   Z operator[](std::initializer_list<int>);
+  Z operator[](auto...);
 };
 X x;
+x[{1,2,3}] = 7;                 // OK, meaning x.operator[]({1,2,3\)}
+x[1,2,3] = 7;                   // OK, meaning x.operator[](1,2,3)
 int a[10];
 a[{1,2,3}] = 7;                 // error: built-in subscript operator
+a[1,2,3] = 7;                   // error: built-in subscript operator
 ```
 — *end example*]

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