具有默认参数构造的 noexcept 说明符
noexcept specifier with default arguments construction
以下面的示例代码为例：
void test(const Item& item = Item()) {
...
}
假设，一旦 item 被传递给函数，这就不会抛出。
问题是：函数应该标记为noexcept还是noexcept(noexcept(Item()))?
IHMO，前者应该可以，但我不确定。非常感谢从标准中引用！
默认参数是函数调用者的快捷符号。所以，当函数执行的时候，构造就已经完成了。
因此，noexcept 应该足够了。
在 standard [dcl.fct.default] 中指出：
If an initializer-clause is specified in a parameter-declaration this
initializer-clause is used as a default argument. Default arguments will be used in calls where trailing arguments are missing.
Example:
the declaration
void point(int = 3, int = 4);
declares a function that can be called with zero, one, or two arguments of type int. It can be called in
any of these ways:
point(1,2); point(1); point();
The last two calls are equivalent to
point(1,4) and point(3,4) , respectively.
还有一个注意事项（在[intro.execution]程序执行中）：
Subexpressions involved in evaluating default arguments (8.3.6) are
considered to be created in the expression that calls the function, not the expression that defines the default
argument
以下面的示例代码为例：
void test(const Item& item = Item()) {
...
}
假设，一旦 item 被传递给函数，这就不会抛出。
问题是：函数应该标记为noexcept还是noexcept(noexcept(Item()))?
IHMO，前者应该可以，但我不确定。非常感谢从标准中引用！
默认参数是函数调用者的快捷符号。所以，当函数执行的时候，构造就已经完成了。
因此，noexcept 应该足够了。
在 standard [dcl.fct.default] 中指出：
If an initializer-clause is specified in a parameter-declaration this initializer-clause is used as a default argument. Default arguments will be used in calls where trailing arguments are missing.
Example: the declaration
void point(int = 3, int = 4);declares a function that can be called with zero, one, or two arguments of type int. It can be called in any of these ways:point(1,2);point(1);point();The last two calls are equivalent topoint(1,4)andpoint(3,4), respectively.
还有一个注意事项（在[intro.execution]程序执行中）：
Subexpressions involved in evaluating default arguments (8.3.6) are considered to be created in the expression that calls the function, not the expression that defines the default argument