为何Clang对容器迭代器的noexcept(++it)与noexcept(*it)处理不一致？

目前尚不明确C++标准是否要求标准容器迭代器的前进操作（++）和解引用操作（*）必须是noexcept的。

不同编译器对此的实现存在差异：

• GCC与MSVC一致将所有标准容器迭代器的上述操作标记为noexcept
• Clang仅对std::vector、std::basic_string的迭代器标记为noexcept，而std::list、std::set、std::map、std::unordered_set、std::unordered_map的迭代器则标记为noexcept(false)

示例代码如下：

#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <vector>
#include <list>
#include <string>
#include <ranges>

template<typename Iterator>
concept nothrow_advancable = noexcept(++std::declval<Iterator&>());

template<typename Iterator>
concept nothrow_dereferencable = noexcept(*std::declval<Iterator&>());

static_assert(nothrow_advancable<std::ranges::iterator_t<std::vector<int>&>>);
static_assert(nothrow_advancable<std::ranges::iterator_t<std::basic_string<char>&>>);
static_assert(nothrow_advancable<std::ranges::iterator_t<std::list<int>&>>); // Clang下不满足noexcept
static_assert(nothrow_advancable<std::ranges::iterator_t<std::set<int>&>>); // Clang下不满足noexcept
static_assert(nothrow_advancable<std::ranges::iterator_t<std::map<int, int>&>>); // Clang下不满足noexcept
static_assert(nothrow_advancable<std::ranges::iterator_t<std::unordered_set<int>&>>); // Clang下不满足noexcept
static_assert(nothrow_advancable<std::ranges::iterator_t<std::unordered_map<int, int>&>>); // Clang下不满足noexcept

static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::vector<int>&>>);
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::basic_string<char>&>>);
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::list<int>&>>); // Clang下不满足noexcept
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::set<int>&>>); // Clang下不满足noexcept
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::map<int, int>&>>); // Clang下不满足noexcept
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::unordered_set<int>&>>); // Clang下不满足noexcept
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::unordered_map<int, int>&>>); // Clang下不满足noexcept

内容的提问来源于stack exchange，提问作者wanghan02