--- title: "Grammar non-terminals for\npostfix-expressions" document: P4176R1 date: 2026-05-12 audience: Core Working Group reply-to: - "Vlad Serebrennikov " paper-type: proposal --- # Abstract 7.6.1 [[expr.post]](https://wg21.link/expr.post) lists all the grammar at the top, while the rest of the subclause resorts to either quoting the grammar or describing it with words. This paper aims to improve the situation, introducing new non-terminals and putting their definitions in the respective subclauses. # Revision history R1: - Adjust proposed wording to address feedback from Jens Maurer. - Address feedback from CWG telecon on 2026-04-28: - Remove (italicized) definition of “function call”. - Replace usages of “subscript expression” and “class member access expression” with the respective grammar terms. - Remove introductory sentences in [[expr.sub]](https://wg21.link/expr.sub) and [[expr.call]](https://wg21.link/expr.call). - Integrate [[expr.post.incr]/2](https://wg21.link/expr.post.incr#2) into [[expr.post.incr]/1.](https://wg21.link/expr.post.incr#1.) - Add new wording to [[expr.prim.paren]](https://wg21.link/expr.prim.paren) to explain that “(possibly parenthesized)” covers more than one level of parentheses. R0: - Initial revision. # Approach - Move grammar definitions of various forms of postfix-expression from 7.6.1.1 [[expr.post.general]](https://wg21.link/expr.post.general) to their respective subclauses, defining new non-terminals. - Define postfix-expressions in terms of new non-terminals. - Make adjustments to the surrounding wording to improve integration between grammar and description of the semantics. - Replace usages of regular font terms with their corresponding grammar productions. For instance, usages of “class member access expression” are replaced with class-member-access-expression. No changes to behavior of programs are intended. Hide removals: Strikethrough: # Proposed wording ## Postfix expressions [[expr.post]](https://wg21.link/expr.post) ### General [[expr.post.general]](https://wg21.link/expr.post.general) Change 7.6.1.1 [[expr.post.general]](https://wg21.link/expr.post.general) paragraph 1 as follows: > 1 Postfix expressions group left-to-right. > > > postfix-expression > > > > : > > > > > primary-expression > > > > > > postfix-expression > > > > > > [ > > > > > > expression-listopt > > > > > > ] > > > > > > subscript-expression > > > > > > postfix-expression > > > > > > ( > > > > > > expression-listopt > > > > > > ) > > > > > > function-call-expression > > > > > > simple-type-specifier > > > > > > ( > > > > > > expression-listopt > > > > > > ) > > > > > > typename-specifier > > > > > > ( > > > > > > expression-listopt > > > > > > ) > > > > > > simple-type-specifier > > > > > > braced-init-list > > > > > > typename-specifier > > > > > > braced-init-list > > > > > > type-conversion-expression > > > > > > postfix-expression > > > > > > . > > > > > > template > > > > > > opt > > > > > > id-expression > > > > > > postfix-expression > > > > > > . > > > > > > splice-expression > > > > > > postfix-expression > > > > > > -> > > > > > > template > > > > > > opt > > > > > > id-expression > > > > > > postfix-expression > > > > > > -> > > > > > > splice-expression > > > > > > class-member-access-expression > > > > > > postfix-expression > > > > > > ++ > > > > > > post-increment-expression > > > > > > postfix-expression > > > > > > -- > > > > > > post-decrement-expression > > > > > > dynamic_cast > > > > > > < > > > > > > type-id > > > > > > > > > > > > > ( > > > > > > expression > > > > > > ) > > > > > > dynamic-cast-expression > > > > > > static_cast > > > > > > < > > > > > > type-id > > > > > > > > > > > > > ( > > > > > > expression > > > > > > ) > > > > > > static-cast-expression > > > > > > reinterpret_cast > > > > > > < > > > > > > type-id > > > > > > > > > > > > > ( > > > > > > expression > > > > > > ) > > > > > > reinterpret-cast-expression > > > > > > const_cast > > > > > > < > > > > > > type-id > > > > > > > > > > > > > ( > > > > > > expression > > > > > > ) > > > > > > const-cast-expression > > > > > > typeid > > > > > > ( > > > > > > expression > > > > > > ) > > > > > > typeid > > > > > > ( > > > > > > type-id > > > > > > ) > > > > > > typeid-expression > > > expression-list > > > > : > > > > > initializer-list Remove 7.6.1.1 [[expr.post.general]](https://wg21.link/expr.post.general) paragraph 2: > 2 > > > [*Note:* The `>` token following the type-id in a `dynamic_cast`, `static_cast`, `reinterpret_cast`, or `const_cast` can be the product of replacing a `>>` token by two consecutive `>` tokens (13.3 [[temp.names]](https://wg21.link/temp.names)). — *end note* ] [ Drafting note: A similar note is added to each kind of cast. ] ### Subscripting [[expr.sub]](https://wg21.link/expr.sub) Change 7.6.1.2 [[expr.sub]](https://wg21.link/expr.sub) paragraph 1 as follows: > > subscript-expression > > > > : > > > > > postfix-expression > > > > > > [ > > > > > > expression-listopt > > > > > > ] > > 1 A *subscript expression* is a postfix expression followed by square brackets containing a possibly empty, comma-separated list of initializer-clauses that The expression-list, if present, constitutes the arguments to the subscript operator. The postfix-expression and the initialization of the object parameter (9.3.4.6 [[dcl.fct]](https://wg21.link/dcl.fct)) of any applicable subscript operator function (12.4.5 [[over.sub]](https://wg21.link/over.sub)) is sequenced before each expression in the expression-list and also before any default argument (9.3.4.7 [[dcl.fct.default]](https://wg21.link/dcl.fct.default)). The initialization of a non-object parameter of a subscript operator function `S`, including every associated value computation and side effect, is indeterminately sequenced with respect to that of any other non-object parameter of `S`. ### Function call [[expr.call]](https://wg21.link/expr.call) Change 7.6.1.3 [[expr.call]](https://wg21.link/expr.call) paragraph 1 as follows: > > function-call-expression > > > > : > > > > > postfix-expression > > > > > > ( > > > > > > expression-listopt > > > > > > ) > > 1 A function call is a postfix expression followed by parentheses containing a possibly empty, comma-separated list of initializer-clauses which The expression-list, if present, constitutes the arguments to the a function designated by the postfix-expression. > > > [*Note:* If the postfix expression postfix-expression is a function name, the appropriate function and the validity of the call are determined according to the rules in 12.2 [[over.match]](https://wg21.link/over.match). — *end note* ] > > The postfix expression postfix-expression *E* shall have function type or function pointer type. For a call to a non-member function or to a static member function, the postfix expression *E* shall be either an lvalue that refers to a function (in which case the function-to-pointer standard conversion (7.3.4 [[conv.func]](https://wg21.link/conv.func)) is suppressed on the postfix expression *E*), or a prvalue of function pointer type. Change 7.6.1.3 [[expr.call]](https://wg21.link/expr.call) paragraph 2 as follows: > 2 If the selected function is non-virtual, or if the id-expression in the class member access expression *E* is a class-member-access-expression whose id-expression is a qualified-id, that function is called. Otherwise, its final overrider (11.7.3 [[class.virtual]](https://wg21.link/class.virtual)) in the dynamic type of the object expression is called; such a call is referred to as a *virtual function call*. > > > [*Note:* [. . .] — *end note* ] ### Explicit type conversion (functional notation) [[expr.type.conv]](https://wg21.link/expr.type.conv) Change 7.6.1.4 [[expr.type.conv]](https://wg21.link/expr.type.conv) paragraph 1 as follows: > > type-conversion-expression > > > > : > > > > > simple-type-specifier > > > > > > ( > > > > > > expression-listopt > > > > > > ) > > > > > > typename-specifier > > > > > > ( > > > > > > expression-listopt > > > > > > ) > > > > > > simple-type-specifier > > > > > > braced-init-list > > > > > > typename-specifier > > > > > > braced-init-list > > 1 A simple-type-specifier or typename-specifier followed by a parenthesized optional expression-list or by a braced-init-list (the initializer) A type-conversion-expression constructs a value of the specified type specified by the simple-type-specifier or typename-specifier. given The braced-init-list or parentheses containing optional expression-list is the initializer. If the type is a placeholder for a deduced class type, it is replaced by the return type of the function selected by overload resolution for class template deduction for the remainder of this subclause. Otherwise, if the type contains a placeholder type, it is replaced by the type determined by placeholder type deduction (9.2.9.7.2 [[dcl.type.auto.deduct]](https://wg21.link/dcl.type.auto.deduct)). Let `T` denote the resulting type. Then: > > - (1.1) If the initializer is a parenthesized single expression expression-list with a single assignment-expression, the type conversion expression is equivalent to the corresponding cast expression (7.6.3 [[expr.cast]](https://wg21.link/expr.cast)). > - (1.2) Otherwise, if `T` is *cv* `void`, the initializer shall be `()` or `{}` (after pack expansion, if any), and the expression is a prvalue of type `void` that performs no initialization. > - (1.3) Otherwise, if `T` is a reference type, the expression has the same effect as direct-initializing an invented variable `t` of type `T` from the initializer and then using `t` as the result of the expression; the result is an lvalue if `T` is an lvalue reference type or an rvalue reference to function type and an xvalue otherwise. > - (1.4) Otherwise, the expression is a prvalue of type `T` whose result object is direct-initialized (9.5 [[dcl.init]](https://wg21.link/dcl.init)) with the initializer. > > If the initializer is a parenthesized optional expression-list, `T` shall not be an array type. > > > [*Example:* [. . .] — *end example* ] [ Drafting note: Do we want to use “(possibly parenthesized)” here, given “the initializer shall be `()` or `{}`” in 1.2? ] ### Class member access [[expr.ref]](https://wg21.link/expr.ref) Change 7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref) paragraph 1 as follows: > > class-member-access-expression > > > > : > > > > > postfix-expression > > > > > > . > > > > > > template > > > > > > opt > > > > > > id-expression > > > > > > postfix-expression > > > > > > . > > > > > > splice-expression > > > > > > postfix-expression > > > > > > -> > > > > > > template > > > > > > opt > > > > > > id-expression > > > > > > postfix-expression > > > > > > -> > > > > > > splice-expression > > 1 A postfix expression followed by a dot `.` or an arrow `->`, optionally followed by the keyword `template`, and then followed by an id-expression or a splice-expression, is a postfix expression. > > > [*Note:* If the keyword `template` is used and followed by an id-expression, the unqualified name is considered to refer to a template (13.3 [[temp.names]](https://wg21.link/temp.names)). If a simple-template-id results and is followed by a `::`, the id-expression is a qualified-id. — *end note* ] [ Drafting note: This note is under consideration by [CWG3180](https://cplusplus.github.io/CWG/issues/3180.html). ] Change footnote 45 referenced from 7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref) paragraph 3: > If the class member access expression class-member-access-expression is evaluated, the subexpression evaluation happens even if the result is unnecessary to determine the value of the entire postfix expression, for example if the id-expression denotes a static member. ### Increment and decrement [[expr.post.incr]](https://wg21.link/expr.post.incr) Change 7.6.1.6 [[expr.post.incr]](https://wg21.link/expr.post.incr) paragraph 1 as follows: > > post-increment-expression > > > > > postfix-expression > > > > > > ++ > > > post-decrement-expression > > > > > postfix-expression > > > > > > -- > > 1 The value of a postfix `++` expression a post-increment-expression or post-decrement-expression *E* is the value obtained by applying the lvalue-to-rvalue conversion (7.3.2 [[conv.lval]](https://wg21.link/conv.lval)) to its operand, which is the postfix-expression. > > > [*Note:* The value obtained is a copy of the original value. — *end note* ] > > The operand shall be a modifiable lvalue. The type of the operand shall be an arithmetic type other than *cv* `bool`, or a pointer to a complete object type. An operand with volatile-qualified type is deprecated; see D.4 [[depr.volatile.type]](https://wg21.link/depr.volatile.type). The value of the operand object is modified (3.1 [[defns.access]](https://wg21.link/defns.access)) as if it were the operand of > > - (1.1) the prefix `++` operator (7.6.2.3 [[expr.pre.incr]](https://wg21.link/expr.pre.incr)) if *E* is a post-increment-expression, or > - (1.2) the prefix `--` operator if *E* is a post-decrement-expression. > > The value computation of the `++` expression *E* is sequenced before the modification of the operand object. With respect to an indeterminately-sequenced function call, the operation of postfix `++` *E* is a single evaluation. > > > [*Note:* Therefore, a function call cannot intervene between the lvalue-to-rvalue conversion and the side effect associated with any single postfix `++` operator post-increment-expression or post-decrement-expression. — *end note* ] > > The result is a prvalue. The type of the result is the cv-unqualified version of the type of the operand. Remove 7.6.1.6 [[expr.post.incr]](https://wg21.link/expr.post.incr) paragraph 2: > 2 The operand of postfix `--` is decremented analogously to the postfix `++` operator. > > > [*Note:* For prefix increment and decrement, see 7.6.2.3 [[expr.pre.incr]](https://wg21.link/expr.pre.incr). — *end note* ] ### Dynamic cast [[expr.dynamic.cast]](https://wg21.link/expr.dynamic.cast) Change 7.6.1.7 [[expr.dynamic.cast]](https://wg21.link/expr.dynamic.cast) paragraph 1 as follows: > > dynamic-cast-expression > > > > : > > > > > dynamic_cast > > > > > > < > > > > > > type-id > > > > > > > > > > > > > ( > > > > > > expression > > > > > > ) > > 1 The result of the expression `dynamic_cast(v)` a dynamic-cast-expression is the result of converting the expression expression `v` to the type `T` designated by the type-id. `T` shall be a pointer or reference to a complete class type, or “pointer to *cv* `void`”. The `dynamic_cast` operator shall not cast away constness (7.6.1.11 [[expr.const.cast]](https://wg21.link/expr.const.cast)). > > > [*Note:* The `>` token following the type-id can be the product of replacing a `>>` token by two consecutive `>` tokens (13.3 [[temp.names]](https://wg21.link/temp.names)). — *end note* ] ### Type identification [[expr.typeid]](https://wg21.link/expr.typeid) Change 7.6.1.8 [[expr.typeid]](https://wg21.link/expr.typeid) paragraph 1 as follows: > > typeid-expression > > > > > typeid > > > > > > ( > > > > > > expression > > > > > > ) > > > > > > typeid > > > > > > ( > > > > > > type-id > > > > > > ) > > 1 The result of a `typeid` expression typeid-expression is an lvalue of static type `const std::type_info` (17.7.3 [[type.info]](https://wg21.link/type.info)) and dynamic type `const std::type_info` or `const` *name* where *name* is an implementation-defined class publicly derived from `std::type_info` which preserves the behavior described in 17.7.3 [[type.info]](https://wg21.link/type.info).48 The lifetime of the object referred to by the lvalue extends to the end of the program. Whether or not the destructor is called for the `std::type_info` object at the end of the program is unspecified. ### Static cast [[expr.static.cast]](https://wg21.link/expr.static.cast) Change 7.6.1.9 [[expr.static.cast]](https://wg21.link/expr.static.cast) paragraph 1 as follows: > > static-cast-expression > > > > static_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > 1 The result of the expression `static_cast(v)` a static-cast-expression is the result of converting the expression expression `v` to the type `T` designated by the type-id. If `T` is an lvalue reference type or an rvalue reference to function type, the result is an lvalue; if `T` is an rvalue reference to object type, the result is an xvalue; otherwise, the result is a prvalue. > > > [*Note:* The `>` token following the type-id can be the product of replacing a `>>` token by two consecutive `>` tokens (13.3 [[temp.names]](https://wg21.link/temp.names)). — *end note* ] ### Reinterpret cast [[expr.reinterpret.cast]](https://wg21.link/expr.reinterpret.cast) Change 7.6.1.10 [[expr.reinterpret.cast]](https://wg21.link/expr.reinterpret.cast) paragraph 1 as follows: > > reinterpret-cast-expression > > > > > reinterpret_cast > > > > > > < > > > > > > type-id > > > > > > > > > > > > > ( > > > > > > expression > > > > > > ) > > 1 The result of the expression `reinterpret_cast(v)` a reinterpret-cast-expression is the result of converting the expression expression `v` to the type `T` designated by the type-id. If `T` is an lvalue reference type or an rvalue reference to function type, the result is an lvalue; if `T` is an rvalue reference to object type, the result is an xvalue; otherwise, the result is a prvalue and the lvalue-to-rvalue, array-to-pointer, and function-to-pointer standard conversions are performed on the expression `v`. Conversions that can be performed explicitly using `reinterpret_cast` are listed below. No other conversion can be performed explicitly using `reinterpret_cast`. > > > [*Note:* The `>` token following the type-id can be the product of replacing a `>>` token by two consecutive `>` tokens (13.3 [[temp.names]](https://wg21.link/temp.names)). — *end note* ] ### Const cast [[expr.const.cast]](https://wg21.link/expr.const.cast) Change 7.6.1.11 [[expr.const.cast]](https://wg21.link/expr.const.cast) paragraph 1 as follows: > > const-cast-expression > > > > > const_cast > > > > > > < > > > > > > type-id > > > > > > > > > > > > > ( > > > > > > expression > > > > > > ) > > 1 The result of the `const_cast(v)` is of type `T`. The result of a const-cast-expression is the result of converting the expression `v` to the type `T` designated by the type-id. If `T` is an lvalue reference to object type, the result is an lvalue; if `T` is an rvalue reference to object type, the result is an xvalue; otherwise, the result is a prvalue and the lvalue-to-rvalue, array-to-pointer, and function-to-pointer standard conversions are performed on the expression `v`. The temporary materialization conversion is not performed on `v`, other than as specified below. Conversions that can be performed explicitly using `const_cast` are listed below. No other conversion shall be performed explicitly using `const_cast`. > > > [*Note:* The `>` token following the type-id can be the product of replacing a `>>` token by two consecutive `>` tokens (13.3 [[temp.names]](https://wg21.link/temp.names)). — *end note* ] ## Overload resolution [[over]](https://wg21.link/over) ### Function call syntax [[over.match.call.general]](https://wg21.link/over.match.call.general) Change 12.2.2.2.1 [[over.match.call.general]](https://wg21.link/over.match.call.general) paragraph 1 as follows: > 1 In a function call (7.6.1.3 [[expr.call]](https://wg21.link/expr.call)) > > > postfix-expression > > > > ( > > > > expression-listopt > > > > ) > > if If the postfix-expression of a function-call-expression names at least one function or function template, overload resolution is applied as specified in 12.2.2.2.2 [[over.call.func]](https://wg21.link/over.call.func). If the postfix-expression denotes an object of class type, overload resolution is applied as specified in 12.2.2.2.3 [[over.call.object]](https://wg21.link/over.call.object). ### Call to designated function [[over.call.func]](https://wg21.link/over.call.func) Apply the following changes to the entire subclause 12.2.2.2.2 [[over.call.func]](https://wg21.link/over.call.func): > 1 Of interest in 12.2.2.2.2 [[over.call.func]](https://wg21.link/over.call.func) are only those function calls in which the postfix-expression ultimately contains an id-expression or splice-expression that designates one or more functions. Such a postfix-expression, perhaps nested arbitrarily deep in parentheses, has one of the following forms: > > > postfix-expression > > > > : > > > > > postfix-expression > > > > > > . > > > > > > id-expression > > > > > > postfix-expression > > > > > > . > > > > > > splice-expression > > > > > > postfix-expression > > > > > > -> > > > > > > id-expression > > > > > > postfix-expression > > > > > > -> > > > > > > splice-expression > > > > > > id-expression > > > > > > splice-expression > > These represent two syntactic subcategories of function calls: qualified function calls and unqualified function calls. > > 2 In qualified function calls, the function is designated by an A *qualified function call* is a function-call-expression whose (possibly parenthesized) postfix-expression is a class-member-access-expression whose id-expression or splice-expression *E* preceded by an `->` or `.` operator designates a function. Since the construct `A->B` is generally equivalent to `(*A).B`, the rest of Clause 12 [[over]](https://wg21.link/over) assumes, without loss of generality, that all member function calls have been normalized to the form that uses an object and the `.` operator. Furthermore, Clause 12 [[over]](https://wg21.link/over) assumes that the postfix-expression that is the left operand of the `.` operator has type “*cv* `T`” where `T` denotes a class.94 The set of candidate functions either is the set found by name lookup (6.5.2 [[class.member.lookup]](https://wg21.link/class.member.lookup)) if *E* is an id-expression or is the set determined as specified in 7.5.9 [[expr.prim.splice]](https://wg21.link/expr.prim.splice) if *E* is a splice-expression. The argument list is the expression-list in the call consists of the arguments of the function-call-expression augmented by the addition of the left operand of the `.` operator in the normalized member function call as the implied object argument (12.2.2 [[over.match.funcs]](https://wg21.link/over.match.funcs)). > > 3 In unqualified function calls, the function is designated by An *unqualified function call* is a function-call-expression whose (possibly parenthesized) postfix-expression is an id-expression or a splice-expression *E* which designates a function. The set of candidate functions either is the set found by name lookup (6.5 [[basic.lookup]](https://wg21.link/basic.lookup)) if *E* is an id-expression or is the set determined as specified in 7.5.9 [[expr.prim.splice]](https://wg21.link/expr.prim.splice) if *E* is a splice-expression. The set of candidate functions consists either entirely of non-member functions or entirely of member functions of some class `T`. In the former case or if *E* is either a splice-expression or the address of an overload set, the argument list is the same as the expression-list in the call consists of the arguments of the function-call-expression. Otherwise, the argument list is the expression-list in the call consists of the arguments of the function-call-expression augmented by the addition of an implied object argument as in a qualified function call. [. . .] > > > [*Example:* [. . .] — *end example* ] [ Drafting note: Does the definition of unqualified function call cover `sizeof(((***func))());`, which is accepted by all implementations ([Compiler Explorer](https://godbolt.org/z/6a7hsYxe6))? ] ### Call to object of class type [[over.call.object]](https://wg21.link/over.call.object) Change 12.2.2.2.3 [[over.call.object]](https://wg21.link/over.call.object) paragraph 1 as follows: > 1 If the postfix-expression *E* in the function call syntax of a function-call-expression evaluates to a class object of type “*cv* `T`”, then the set of candidate functions includes at least the function call operators of `T`. The function call operators of `T` are the results of a search for the name `operator()` in the scope of `T`. ### Function call [[over.call]](https://wg21.link/over.call) Change 12.4.4 [[over.call]](https://wg21.link/over.call) paragraph 1 as follows: > 1 A *function call operator function* is a function named `operator()` that is a member function with an arbitrary number of parameters. It may have default arguments. For an expression of the form a function-call-expression > > > postfix-expression > > > > ( > > > > expression-listopt > > > > ) > > where whose the postfix-expression is of class type, the operator function is selected by overload resolution (12.2.2.2.3 [[over.call.object]](https://wg21.link/over.call.object)). If a surrogate call function is selected, let *e* be the result of invoking the corresponding conversion operator function on the postfix-expression; > > the expression is interpreted as > > > *e* > > > > ( > > > > expression-listopt > > > > ) > > Otherwise, the expression is interpreted as > > > postfix-expression > > > > . > > > > operator () > > > > ( > > > > expression-listopt > > > > ) [ Drafting note: Should we keep quoting the grammar of function-call-expression to make it clear where expression-list comes from? The same applies to [[over.sub]](https://wg21.link/over.sub) changes below. ] ### Subscripting [[over.sub]](https://wg21.link/over.sub) Change 12.4.5 [[over.sub]](https://wg21.link/over.sub) paragraph 1 as follows: > 1 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 a subscript-expression > > > postfix-expression > > > > [ > > > > expression-listopt > > > > ] > > the operator function is selected by overload resolution (12.2.2.3 [[over.match.oper]](https://wg21.link/over.match.oper)). If a member function is selected, the expression is interpreted as > > > postfix-expression > > > > . > > > > operator > > > > [] > > > > ( > > > > expression-listopt > > > > ) ### Class member access [[over.ref]](https://wg21.link/over.ref) Change 12.4.6 [[over.ref]](https://wg21.link/over.ref) paragraph 1 as follows: > 1 A *class member access operator function* is a function named `operator->` that is a non-static member function taking no non-object parameters. For an expression a class-member-access-expression of the form > > > postfix-expression > > > > -> > > > > template > > > > opt > > > > id-expression > > the operator function is selected by overload resolution (12.2.2.3 [[over.match.oper]](https://wg21.link/over.match.oper)), and the expression is interpreted as > > > ( > > > > postfix-expression > > > > . > > > > operator > > > > -> > > > > () > > > > ) > > > > -> > > > > template > > > > opt > > > > id-expression > > Analogously, for an expression a class-member-access-expression of the form > > > postfix-expression > > > > -> > > > > splice-expression > > the operator function is selected by overload resolution, and the expression is interpreted as > > > ( > > > > postfix-expression > > > > . > > > > operator > > > > -> > > > > () > > > > ) > > > > -> > > > > splice-expression ## The rest of the core language wording ### One-defintion rule [[basic.def.odr]](https://wg21.link/basic.def.odr) Change 6.3 [[basic.def.odr]](https://wg21.link/basic.def.odr) paragraph 3 as follows: > 3 An expression or conversion is *potentially evaluated* unless it is an unevaluated operand (7.2.3 [[expr.context]](https://wg21.link/expr.context)), a subexpression thereof, or a conversion in an initialization or conversion sequence in such a context. The set of *potential results* of an expression *E* is defined as follows: > > - [. . .] > - (3.3) If *E* is a class member access expression (7.6.1.5) class-member-access-expression of the form *E*1 `.` `template`opt *E*2, where *E*2 designates a non-static data member or a direct base class relationship, the set contains the potential results of *E*1. > - (3.4) If *E* is a class member access expression class-member-access-expression naming a static data member, the set contains the id-expression designating the data member. > - [. . .] Change 6.3 [[basic.def.odr]](https://wg21.link/basic.def.odr) paragraph 5 as follows: > 5 A variable is named by an expression if the expression is an id-expression or splice-expression (7.5.9 [[expr.prim.splice]](https://wg21.link/expr.prim.splice)) that designates it. A variable `x` that is named by a potentially evaluated expression *N* that appears at a point *P* is *odr-used* by *N* unless > > - (5.1) `x` is a reference that is usable in constant expressions at *P* ([[expr.const.init]](https://wg21.link/expr.const.init)), or > - (5.2) *N* is an element of the set of potential results of an expression *E*, where > - (5.2.1) *E* is a discarded-value expression (7.2.3 [[expr.context]](https://wg21.link/expr.context)) to which the lvalue-to-rvalue conversion is not applied, or > - (5.2.2) `x` is a non-volatile object that is usable in constant expressions at *P* and has no mutable subobjects, and > - (5.2.2.1) *E* is a class member access expression (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expression naming a non-static data member of reference type and whose object expression has non-volatile-qualified type, or > - (5.2.2.2) the lvalue-to-rvalue conversion (7.3.2 [[conv.lval]](https://wg21.link/conv.lval)) is applied to *E* and *E* has non-volatile-qualified non-class type. > > > [*Example:* [. . .] — *end example* ] Change 6.3 [[basic.def.odr]](https://wg21.link/basic.def.odr) paragraph 7 as follows: > 7 `*this` is odr-used if `this` appears as a potentially evaluated expression (including as the result of any implicit transformation to a class member access expression class-member-access-expression (7.5.5.1 [[expr.prim.id.general]](https://wg21.link/expr.prim.id.general))). ### Unqualified name lookup [[basic.lookup.unqual]](https://wg21.link/basic.lookup.unqual) Change 6.5.3 [[basic.lookup.unqual]](https://wg21.link/basic.lookup.unqual) paragraph 4 as follows: > 4 An *unqualified name* is a name that does not immediately follow a nested-name-specifier or the `.` or `->` in a class member access expression (7.6.1.5) class-member-access-expression, possibly after a `template` keyword or `~`. Unless otherwise specified, such a name undergoes unqualified name lookup from the point where it appears. ### Argument-dependent name lookup [[basic.lookup.argdep]](https://wg21.link/basic.lookup.argdep) Change 6.5.4 [[basic.lookup.argdep]](https://wg21.link/basic.lookup.argdep) paragraph 1 as follows: > 1 When the postfix-expression in a function call (7.6.1.3 [[expr.call]](https://wg21.link/expr.call)) function-call-expression is an unqualified-id, and unqualified lookup (6.5.3 [[basic.lookup.unqual]](https://wg21.link/basic.lookup.unqual)) for the name in the unqualified-id does not find any > > - (1.1) declaration of a class member, or > - (1.2) function declaration inhabiting a block scope, or > - (1.3) declaration not of a function or function template > > then lookup for the name also includes the result of *argument-dependent lookup* in a set of associated namespaces that depends on the types of the arguments (and for type template template arguments, the namespace of the template argument), as specified below. > > > [*Example:* [. . .] — *end example* ] Change 6.5.4 [[basic.lookup.argdep]](https://wg21.link/basic.lookup.argdep) paragraph 2 as follows: > 2 > > > [*Note:* For purposes of determining (during parsing) whether an expression is a postfix-expression for a function call of a function-call-expression, the usual name lookup rules apply. In some cases a name followed by `<` is treated as a template-name even though name lookup did not find a template-name (see 13.3 [[temp.names]](https://wg21.link/temp.names)). For example, > > > > ```cpp > > int h; > > void g(); > > namespace N { > > struct A {}; > > template int f(T); > > template int g(T); > > template int h(T); > > } > > > > int x = f(N::A()); // OK, lookup of f finds nothing, f treated as template name > > int y = g(N::A()); // OK, lookup of g finds a function, g treated as template name > > int z = h(N::A()); // error: h< does not begin a template-id > > ``` > > > > The rules have no effect on the syntactic interpretation of an expression. For example, > > > > ```cpp > > typedef int f; > > namespace N { > > struct A { > > friend void f(A &); > > operator int(); > > void g(A a) { > > int i = f(a); // f is the typedef, not the friend function: equivalent to int(a) > > } > > }; > > } > > ``` > > > > Because the expression is not a function call function-call-expression, argument-dependent name lookup does not apply and the friend function `f` is not found. — *end note* ] ### Qualified name lookup [[basic.lookup.qual.general]](https://wg21.link/basic.lookup.qual.general) Change 6.5.5.1 [[basic.lookup.qual.general]](https://wg21.link/basic.lookup.qual.general) paragraph 2 as follows: > 2 A *member-qualified name* is the (unique) component name (7.5.5.2 [[expr.prim.id.unqual]](https://wg21.link/expr.prim.id.unqual)), if any, of > > - (2.1) an unqualified-id or > - (2.2) a nested-name-specifier of the form type-name `::` or namespace-name `::` > > in the id-expression of a class member access expression (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expression. [. . .] > > > [*Note:* [. . .] — *end note* ] > > > [*Example:* [. . .] — *end example* ] ### Dynamic storage duration [[basic.stc.dynamic]](https://wg21.link/basic.stc.dynamic) Change 6.8.6.5.1 [[basic.stc.dynamic.general]](https://wg21.link/basic.stc.dynamic.general) paragraph 2 as follows: > 2 [. . .] > > > [*Note:* he implicit declarations do not introduce the names `std`, `std::size_t`, `std::align_val_t`, or any other names that the library uses to declare these names. Thus, a new-expression, delete-expression, or function call function-call-expression that refers to one of these functions without importing or including the header `` (17.6.2 [[new.syn]](https://wg21.link/new.syn)) or importing a C++ library module (16.4.2.4 [[std.modules]](https://wg21.link/std.modules)) is well-formed. However, referring to `std` or `std::size_t` or `std::align_val_t` is ill-formed unless a standard library declaration (17.2.1 [[cstddef.syn]](https://wg21.link/cstddef.syn), 17.6.2 [[new.syn]](https://wg21.link/new.syn), 16.4.2.4 [[std.modules]](https://wg21.link/std.modules)) of that name precedes (6.5.1 [[basic.lookup.general]](https://wg21.link/basic.lookup.general)) the use of that name. — *end note* ] > > [. . .] ### Sequential execution [[intro.execution]](https://wg21.link/intro.execution) Change 6.10.1 [[intro.execution]](https://wg21.link/intro.execution) paragraph 11 as follows: > 11 When invoking a function *f* (whether or not the function is inline), every argument expression and the postfix expression postfix-expression designating *f* are sequenced before every precondition assertion of *f* (9.4.1 [[dcl.contract.func]](https://wg21.link/dcl.contract.func)), which in turn are sequenced before every expression or statement in the body of *f*, which in turn are sequenced before every postcondition assertion of *f*. ### Value category [[basic.lval]](https://wg21.link/basic.lval) Change 7.2.1 [[basic.lval]](https://wg21.link/basic.lval) paragraph 4 as follows: > > [*Note:* An expression is an xvalue if it is: > > > > - [. . .] > > - (4.5) a class member access expression class-member-access-expression designating a non-static data member of non-reference type in which the object expression is an xvalue (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)), or > > - [. . .] > > > > [. . .] > > > > > [*Example:* [. . .] — *end example* ] > > > >   — *end note* ] ### Parentheses [[expr.prim.paren]](https://wg21.link/expr.prim.paren) Add a new paragraph at the end of 7.5.4 [[expr.prim.paren]](https://wg21.link/expr.prim.paren): > 1 A parenthesized expression `(`*E*`)` is a primary expression whose type, result, and value category are identical to those of *E*. The parenthesized expression can be used in exactly the same contexts as those where *E* can be used, and with the same meaning, except as otherwise indicated. > > n A possibly parenthesized expression may be nested arbitrarily deep in parentheses. [ Drafting note: Do we need a cross-reference to [[implimits]/1.4](https://wg21.link/implimits#1.4)? ] ### Names [[expr.prim.id.general]](https://wg21.link/expr.prim.id.general) Change 7.5.5.1 [[expr.prim.id.general]](https://wg21.link/expr.prim.id.general) paragraph 2 as folows: > 2 If an id-expression *E* denotes a non-static non-type member of some class `C` at a point where the current class (7.5.3 [[expr.prim.this]](https://wg21.link/expr.prim.this)) is `X` and > > - (2.1) *E* is potentially evaluated or `C` is `X` or a base class of `X`, and > - (2.2) *E* is not the id-expression of a class member access expression (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expression, and > - (2.3) *E* is not the id-expression of a reflect-expression (7.6.2.10 [[expr.reflect]](https://wg21.link/expr.reflect)), and > - (2.4) if *E* is a qualified-id, *E* is not the un-parenthesized operand of the unary `&` operator (7.6.2.2 [[expr.unary.op]](https://wg21.link/expr.unary.op)), > > the id-expression is transformed into a class member access expression class-member-access-expression using `(*this)` as the object expression. If this transformation occurs in the predicate of a precondition assertion of a constructor of `X` or a postcondition assertion of a destructor of `X`, the expression is ill-formed. > > > [*Note:* If `C` is not `X` or a base class of `X`, the class member access expression class-member-access-expression is ill-formed. Also, if the id-expression occurs within a static or explicit object member function, the class member access is ill-formed. — *end note* ] > > This transformation does not apply in the template definition context (13.8.3.2 [[temp.dep.type]](https://wg21.link/temp.dep.type)). > > > [*Example:* [. . .] — *end example* ] Change 7.5.5.1 [[expr.prim.id.general]](https://wg21.link/expr.prim.id.general) paragraph 3 as folows: > 3 If an id-expression *E* denotes a variant member *M* of an anonymous union (11.5.2 [[class.union.anon]](https://wg21.link/class.union.anon)) *U*: > > - (3.1) If *U* is a non-static data member, *E* refers to *M* as a member of the lookup context of the terminal name of *E* (after any implicit transformation to a class member access expression class-member-access-expression). [*Example:* `o.x` is interpreted as `o.`*u*`.x`, where *u* names the anonymous union member. — *end example* ] > - [. . .] ### Unqualified names [[expr.prim.id.unqual]](https://wg21.link/expr.prim.id.unqual) Change 7.5.5.2 [[expr.prim.id.unqual]](https://wg21.link/expr.prim.id.unqual) paragraph 4 as folows: > 4 if > > - (4.1) the unqualified-id appears in a lambda-expression at program point *P*, > - (4.2) the entity is a local entity (6.1 [[basic.pre]](https://wg21.link/basic.pre)) or a variable declared by an init-capture (7.5.6.3 [[expr.prim.lambda.capture]](https://wg21.link/expr.prim.lambda.capture)), > - (4.3) naming the entity within the compound-statement of the innermost enclosing lambda-expression of *P*, but not in an unevaluated operand, would refer to an entity captured by copy in some intervening lambda-expression, and > - (4.4) *P* is in the function parameter scope, but not the parameter-declaration-clause, of the innermost such lambda-expression *E*, > > then the type of the expression is the type of a class member access expression (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expression naming the non-static data member that would be declared for such a capture in the object parameter (9.3.4.6 [[dcl.fct]](https://wg21.link/dcl.fct)) of the function call operator of *E*. > > > [*Note:* [. . .] — *end note* ] > > > [*Example:* [. . .] — *end example* ] ### Destruction [[expr.prim.id.dtor]](https://wg21.link/expr.prim.id.dtor) Change 7.5.5.5 [[expr.prim.id.dtor]](https://wg21.link/expr.prim.id.dtor) paragraph 2 as follows: > 2 If the id-expression names a pseudo-destructor, `T` shall be a scalar type and the id-expression shall appear as the right operand of a class member access (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expression that forms the postfix-expression of a function call (7.6.1.3 [[expr.call]](https://wg21.link/expr.call)) function-call-expression. ### Expression splicing [[expr.prim.splice]](https://wg21.link/expr.prim.splice) Change 7.5.9 [[expr.prim.splice]](https://wg21.link/expr.prim.splice) paragraph 4 as follows: > 4 For a splice-expression of the form template splice-specialization-specifier, the splice-specifier of the splice-specialization-specifier shall designate a template *T*. > > - [. . .] > > > [*Note:* Class members are accessible from any point when designated by splice-expressions (11.8.3 [[class.access.base]](https://wg21.link/class.access.base)). A class member access expression (7.6.1.5) class-member-access-expression whose right operand is a splice-expression is ill-formed if the left operand (considered as a pointer) cannot be implicitly converted to a pointer to the designating class of the right operand. — *end note* ] ### Unary operators [[expr.unary.op]](https://wg21.link/expr.unary.op) Change 7.6.2.2 [[expr.unary.op]](https://wg21.link/expr.unary.op) paragraph 3 as follows: > 3 The operand of the unary `&` operator shall be an lvalue of some type `T`. > > - (3.1) If the operand is a qualified-id or splice-expression designating a non-static member m, other than an explicit object member function, `m` shall be a direct member of some class `C` that is not an anonymous union. The result has type “pointer to member of class `C` of type `T`” and designates `C::m`. [*Note:* A qualified-id that names a member of a namespace-scope anonymous union is considered to be a class member access expression (7.5.5.1) class-member-access-expression and cannot be used to form a pointer to member. — *end note* ] > - [. . .] ### Comma operator [[expr.comma]](https://wg21.link/expr.comma) Change 7.6.20 [[expr.comma]](https://wg21.link/expr.comma) paragraph 2 as follows: > 2 > > > [*Note:* In contexts where the comma token is given special meaning (e.g., function calls (7.6.1.3) function-call-expressions, subscript expressions (7.6.1.2) subscript-expressions, lists of initializers (9.5) initializer-lists, or template-argument-lists (13.3 [[temp.names]](https://wg21.link/temp.names))), the comma operator as described in this subclause can appear only in parentheses. > > > > > [*Example:* [. . .] — *end example* ] > > > >   — *end note* ] ### Core constant expressions [[expr.const.core]](https://wg21.link/expr.const.core) Change [[expr.const.core]](https://wg21.link/expr.const.core) paragraph 2 as follows: > 2 An expression *E* is a *core constant expression* unless the evaluation of *E*, following the rules of the abstract machine (6.10.1 [[intro.execution]](https://wg21.link/intro.execution)), would evaluate one of the following: > > - (2.1) `this` (7.5.3 [[expr.prim.this]](https://wg21.link/expr.prim.this)), except > - [. . .] > - (2.1.2) when appearing as the postfix-expression of an implicit or explicit class member access expression (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expression; > - [. . .] > - [. . .] > - (2.18) an invocation of a destructor (11.4.7 [[class.dtor]](https://wg21.link/class.dtor)) or a function call function-call-expression whose postfix-expression names a pseudo-destructor (7.6.1.3 [[expr.call]](https://wg21.link/expr.call)), in either case for an object whose lifetime did not begin within the evaluation of *E*; > - [. . .] ### Default arguments [[dcl.fct.default]](https://wg21.link/dcl.fct.default) Change 9.3.4.7 [[dcl.fct.default]](https://wg21.link/dcl.fct.default) paragraph 9 as follows: > 9 A default argument is evaluated each time the function is called with no argument for the corresponding parameter. A parameter shall not appear as a potentially evaluated expression in a default argument. > > > [*Note:* [. . .] — *end note* ] > > > [*Example:* [. . .] — *end example* ] > > A non-static member shall not be designated in a default argument unless > > - (9.1) it is designated by the id-expression or splice-expression of a class member access expression (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expression, > - [. . .] > > [. . .] ### Defaulted comparison operator functions [[class.compare.default]](https://wg21.link/class.compare.default) Change 11.10.1 [[class.compare.default]](https://wg21.link/class.compare.default) paragraph 5 as follows: > 5 The direct base class subobjects of `C`, in the order of their declaration in the base-specifier-list of `C`, followed by the non-static data members of `C`, in the order of their declaration in the member-specification of `C`, form a list of subobjects. In that list, any subobject of array type is recursively expanded to the sequence of its elements, in the order of increasing subscript. Let `x`*i* be an lvalue denoting the *i*th element in the expanded list of subobjects for an object `x` (of length *n*), where `x`*i* is formed by a sequence of derived-to-base conversions (12.2.4.2 [[over.best.ics]](https://wg21.link/over.best.ics)), class member access expressions (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expressions, and array subscript expressions (7.6.1.2 [[expr.sub]](https://wg21.link/expr.sub)) subscript-expressions applied to `x`. ### Names of template specialization [[temp.names]](https://wg21.link/temp.names) Change [[temp.names]](https://wg21.link/temp.names) paragraph 3 as follows: > 3 A `<` is interpreted as the delimiter of a template-argument-list if either > > - (3.1) it follows a splice-specifier that either > - (3.1.1) appears in a type-only context or > - (3.1.1) is preceded by `template` or `typename`, or > - (3.2) it follows a name that is not a conversion-function-id and > - (3.2.1) that follows the keyword `template` or a `~` after a nested-name-specifier or in a class member access expression class-member-access-expression, or > - [. . .] > > > [*Note:* [. . .] — *end note* ] > > > [*Example:* [. . .] — *end example* ] ### Dependent names [[temp.dep.general]](https://wg21.link/temp.dep.general) Change 13.8.3.1 [[temp.dep.general]](https://wg21.link/temp.dep.general) paragraph 2 as follows: > 2 A dependent call *dependent call* is an expression a function-call-expression, possibly formed as a non-member candidate for an operator (12.2.2.3 [[over.match.oper]](https://wg21.link/over.match.oper)), of the form: > > > postfix-expression > > > > ( > > > > expression-listopt > > > > ) > > where the whose postfix-expression is an unqualified-id and > > - (2.1) any of the expressions in the expression-list is a pack expansion (13.7.4 [[temp.variadic]](https://wg21.link/temp.variadic)), or > - (2.2) any of the expression or brace-init-lists in the expression-list is type-dependent (13.8.3.3 [[temp.dep.expr]](https://wg21.link/temp.dep.expr)), or > - (2.3) the unqualified-id is a template-id in which any of the template arguments depends on a template parameters. > > The component name of an unqualified-id (7.5.5.2 [[expr.prim.id.unqual]](https://wg21.link/expr.prim.id.unqual)) is dependent if > > - (2.4) it is a conversion-function-id whose conversion-type-id is dependent, or > - (2.5) it is `operator=` and the current class is a templated entity, or > - (2.6) the unqualified-id is the postfix-expression in a dependent call. > > > [*Note:* [. . .] — *end note* ] ### Type-dependent expressions [[temp.dep.expr]](https://wg21.link/temp.dep.expr) Do not change 13.8.3.3 [[temp.dep.expr]](https://wg21.link/temp.dep.expr) paragraph 3: > 3 [. . .] Expressions of the following forms are type-dependent only if the type specified by the type-id, simple-type-specifier, typename-specifier, or new-type-id is dependent, even if any subexpression is type-dependent: > > > simple-type-specifier > > > > ( > > > > expression-listopt > > > > ) > > > > simple-type-specifier > > > > braced-init-list > > > > typename-specifier > > > > ( > > > > expression-listopt > > > > ) > > > > typename-specifier > > > > braced-init-list > > > > :: > > > > opt > > > > new > > > > new-placementopt > > > > new-type-id > > > > new-initializeropt > > > > :: > > > > opt > > > > new > > > > new-placementopt > > > > ( > > > > type-id > > > > ) > > > > new-initializeropt > > > > dynamic_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > > > static_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > > > const_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > > > reinterpret_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > > > ( > > > > type-id > > > > ) > > > > cast-expression Change 13.8.3.3 [[temp.dep.expr]](https://wg21.link/temp.dep.expr) paragraph 4 as follows: > 4 Expressions of the following forms are never type-dependent (because the type of the expression cannot be dependent): > > > literal > > > > sizeof > > > > unary-expression > > > > sizeof > > > > ( > > > > type-id > > > > ) > > > > sizeof > > > > ... > > > > ( > > > > identifier > > > > ) > > > > alignof > > > > ( > > > > type-id > > > > ) > > > > `typeid` > > `(` > > *expression* > > `)` > > > > `typeid` > > `(` *type-id* > > `)` > > > > *typeid-expression* > > > > :: > > > > opt > > > > delete > > > > cast-expression > > > > :: > > > > opt > > > > delete > > > > [ > > > > ] > > > > cast-expression > > > > throw > > > > assignment-expressionopt > > > > noexcept > > > > ( > > > > expression > > > > ) > > > > requires-expression > > > > reflect-expression > > > [*Note:* For the standard library macro `offsetof`, see 17.2 [[support.types]](https://wg21.link/support.types). — *end note* ] Change 13.8.3.3 [[temp.dep.expr]](https://wg21.link/temp.dep.expr) paragraph 5 as follows: > 5 A class member access expression (7.6.1.5 [[expr.ref]](https://wg21.link/expr.ref)) class-member-access-expression is type-dependent if > > - (5.1) the terminal name of its id-expression, if any, is dependent, > - (5.2) its splice-expression, if any, is type-dependent, or > - (5.3) the expression refers to a member of the current instantiation and the type of the referenced member is dependent. ### Value-dependent expression [[temp.dep.constexpr]](https://wg21.link/temp.dep.constexpr) Do not change 13.8.3.4 [[temp.dep.constexpr]](https://wg21.link/temp.dep.constexpr) paragraphs 2 and 3: > 2 [. . .] Expressions of the following form are value-dependent if the unary-expression or expression is type-dependent or the type-id is dependent: > > > sizeof > > > > unary-expression > > > > sizeof > > > > ( > > > > type-id > > > > ) > > > > typeid > > > > ( > > > > expression > > > > ) > > > > typeid > > > > ( > > > > type-id > > > > ) > > > > alignof > > > > ( > > > > type-id > > > > ) > > > [*Note:* For the standard library macro `offsetof`, see 17.2 [[support.types]](https://wg21.link/support.types). — *end note* ] > > 3 Expressions of the following form are value-dependent if either the type-id, simple-type-specifier, or typename-specifier is dependent or the expression or cast-expression is value-dependent or any expression in the expression-list is value-dependent or any assignment-expression in the braced-init-list is value-dependent: > > > simple-type-specifier > > > > ( > > > > expression-listopt > > > > ) > > > > typename-specifier > > > > ( > > > > expression-listopt > > > > ) > > > > simple-type-specifier > > > > braced-init-list > > > > typename-specifier > > > > braced-init-list > > > > static_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > > > const_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > > > reinterpret_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > > > dynamic_cast > > > > < > > > > type-id > > > > > > > > > ( > > > > expression > > > > ) > > > > ( > > > > type-id > > > > ) > > > > cast-expression ### Deducing template arguments from a type [[temp.deduct.type]](https://wg21.link/temp.deduct.type) Change 13.10.3.6 [[temp.deduct.type]](https://wg21.link/temp.deduct.type) paragraph 23 as follows: > 23 The template-argument corresponding to a template template parameter is deduced from the type of the template-argument of a class template specialization used in the argument list of a function call (12.2.2.2.2 [[over.call.func]](https://wg21.link/over.call.func)). > > > [*Example:* [. . .] — *end example* ] ### Exception specifications [[except.spec]](https://wg21.link/except.spec) Change 14.5 [[except.spec]](https://wg21.link/except.spec) paragraph 5 as follows: > 5 An expression *E* is *potentially-throwing* if > > - (5.1) *E* is a function call (7.6.1.3 [[expr.call]](https://wg21.link/expr.call)) function-call-expression whose postfix-expression has a function type, or a pointer-to-function type, with a potentially-throwing exception specification, or > - [. . .] ## Library wording ### Algorithm function objects [[alg.func.obj]](https://wg21.link/alg.func.obj) Change 16.3.3.4 [[alg.func.obj]](https://wg21.link/alg.func.obj) paragraph 2 as follows: > 2 For an algorithm function object `o`, let *S* be the corresponding set of function templates. Then for any sequence of arguments `args . . .`, `o(args . . . )` is expression-equivalent to `s(args . . . )`, where the result of name lookup for `s` is the overload set *S*. > > > [*Note:* Algorithm function objects are not found by argument-dependent name lookup (6.5.4 [[basic.lookup.argdep]](https://wg21.link/basic.lookup.argdep)). When found by unqualified name lookup (6.5.3 [[basic.lookup.unqual]](https://wg21.link/basic.lookup.unqual)) for the postfix-expression in a function call (7.6.1.3 [[expr.call]](https://wg21.link/expr.call)) function-call-expression, they inhibit argument-dependent name lookup. > > > > > [*Example:* > > > > > > ```cpp > > > void foo() { > > > using namespace std::ranges; > > > std::vector vec{1,2,3}; > > > find(begin(vec), end(vec), 2); // #1 > > > } > > > ``` > > > > > > The function call expression function-call-expression at #1 invokes `std::ranges::find`, not `std::find`. — *end example* ] > > > >   — *end note* ] ### Creation [[support.srcloc.cons]](https://wg21.link/support.srcloc.cons) Change 17.8.2.2 [[support.srcloc.cons]](https://wg21.link/support.srcloc.cons) paragraph 1 as follows: > ```cpp > static consteval source_location current() noexcept; > ``` > > > 1 *Returns*: > > > > - (1.1) When invoked by a function call function-call-expression whose postfix-expression is a (possibly parenthesized) id-expression naming `current`, returns a `source_location` with an implementation-defined value. [. . .] > > - [. . .] ### Function objects [[function.objects.general]](https://wg21.link/function.objects.general) Change 22.10.1 [[function.objects.general]](https://wg21.link/function.objects.general) paragraph 1 as follows: > 1 A function object type is an object type (6.9.1 [[basic.types.general]](https://wg21.link/basic.types.general)) that can be the type of the postfix-expression in a function call (7.6.1.3 [[expr.call]](https://wg21.link/expr.call), 12.2.2.2 [[over.match.call]](https://wg21.link/over.match.call)) function-call-expression.174 ## Annex C ### Clause 7: expressions [[diff.cpp20.expr]](https://wg21.link/diff.cpp20.expr) Change C.2.3 [[diff.cpp20.expr]](https://wg21.link/diff.cpp20.expr) paragraph 2 as follows: > **Affected subclause:** 7.6.1.2 [[expr.sub]](https://wg21.link/expr.sub) > > **Change:** Change the meaning of comma in subscript expressions subscript-expressions. > > **Rationale:** Enable repurposing a deprecated syntax to support multidimensional indexing. > > **Effect on original feature:** Valid C++ 2020 code that uses a comma expression within a subscript expression subscript-expression may fail to compile. > > > [*Example:* > > > > ```cpp > > arr[1, 2] // was equivalent to arr[(1, 2)], > > // now equivalent to arr.operator[](1, 2) or ill-formed > > ``` > > > >   — *end example* ]