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 or typename-specifier 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 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.
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 with the initializer.
If the initializer is a parenthesized optional expression-list, the specified type shall not be an array type.