7 Expressions [expr]

7.6 Compound expressions [expr.compound]

7.6.1 Postfix expressions [expr.post]

7.6.1.4 Explicit type conversion (functional notation) [expr.type.conv]

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A simple-type-specifier ([dcl.type.simple]) or typename-specifier ([temp.res]) followed by a parenthesized optional expression-list or by a braced-init-list (the initializer) constructs a value of the specified type given 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 ([over.match.class.deduct]) 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 ([dcl.type.auto.deduct]).
[Example 1: struct A {}; void f(A&); // #1 void f(A&&); // #2 A& g(); void h() { f(g()); // calls #1 f(A(g())); // calls #2 with a temporary object f(auto(g())); // calls #2 with a temporary object } — end example]
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If the initializer is a parenthesized single expression, the type conversion expression is equivalent to the corresponding cast expression ([expr.cast]).
Otherwise, if the type is cv void and the initializer is () or {} (after pack expansion, if any), the expression is a prvalue of type void that performs no initialization.
Otherwise, the expression is a prvalue of the specified type whose result object is direct-initialized ([dcl.init]) with the initializer.
If the initializer is a parenthesized optional expression-list, the specified type shall not be an array type.