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 section.
If the initializer is a parenthesized single expression, the type conversion expression is equivalent (in definedness, and if defined in meaning) to the corresponding cast expression ([expr.cast]). If the type is (possibly cv-qualified) void and the initializer is (), the expression is a prvalue of the specified type 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. For an expression of the form T(), T shall not be an array type.