fix hash_* visualizer issue

[fsb4000]

Fixes #2783

test:

#define _SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS
#include <hash_set>
#include <hash_map>
using namespace std;
int main() {
	stdext::hash_set<int> hs = { 1,2,3 };
	stdext::hash_multiset<int> hms = { 1,1,2,3 };
	stdext::hash_map<int, char> hm = { {1, 'a'}, {2,'b'} };
	stdext::hash_multimap<int, char> hmm = { {1, 'a'}, {1, 'c'}, {2,'b'} };
}

_Traitsobj class:

STL/stl/inc/hash_map

Lines 41 to 110 in e178ea2

	class _Hmap_traits : public _Tr { // traits required to make _Hash behave like a map
	public:
	using key_type = _Kty;
	using value_type = pair<const _Kty, _Ty>;
	using _Mutable_value_type = pair<_Kty, _Ty>;
	using key_compare = _Tr;
	using allocator_type = _Alloc;
	#if _HAS_CXX17
	using node_type =
	_STD _Node_handle<_STD _List_node<value_type, typename _STD allocator_traits<_Alloc>::void_pointer>, _Alloc,
	_STD _Node_handle_map_base, _Kty, _Ty>;
	#endif // _HAS_CXX17
	static constexpr bool _Multi = _Mfl;
	static constexpr bool _Standard = false;
	template <class... _Args>
	using _In_place_key_extractor = _STD _In_place_key_extract_map<_Kty, _Args...>;
	template <class>
	using _Deduce_key = const _Kty&;
	using key_equal = _Tr;
	_Hmap_traits() = default;
	_Hmap_traits(const _Tr& _Traits) noexcept(_STD is_nothrow_copy_constructible_v<_Tr>) : _Tr(_Traits) {}
	class value_compare {
	public:
	using first_argument_type = value_type;
	using second_argument_type = value_type;
	using result_type = bool;
	_NODISCARD bool operator()(const value_type& _Left, const value_type& _Right) const
	noexcept(noexcept(_Keycompobj(_Left.first, _Right.first))) {
	// test if _Left precedes _Right by comparing just keys
	return _Keycompobj(_Left.first, _Right.first);
	}
	value_compare(const key_compare& _Keycomparg) noexcept(_STD is_nothrow_copy_constructible_v<key_compare>)
	: _Keycompobj(_Keycomparg) {}
	key_compare _Keycompobj;
	};
	template <class _Ty1, class _Ty2>
	_NODISCARD static const _Kty& _Kfn(const pair<_Ty1, _Ty2>& _Val) noexcept { // extract key from element value
	return _Val.first;
	}
	template <class _Ty1, class _Ty2>
	_NODISCARD static const _Ty2& _Nonkfn(const pair<_Ty1, _Ty2>& _Val) noexcept {
	// extract non-key from element value
	return _Val.second;
	}
	_NODISCARD float& _Get_max_bucket_size() noexcept {
	return _Max_buckets;
	}
	_NODISCARD const float& _Get_max_bucket_size() const noexcept {
	return _Max_buckets;
	}
	void swap(_Hmap_traits& _Rhs) noexcept(_Is_nothrow_swappable<_Tr>::value) {
	_Swap_adl(static_cast<_Tr&>(*this), static_cast<_Tr&>(_Rhs));
	_STD swap(_Max_buckets, _Rhs._Max_buckets);
	}
	float _Max_buckets = 0.0F; // current maximum bucket size
	};

_Tr class:

STL/stl/inc/xhash

Lines 59 to 87 in 37b5120

	class hash_compare { // traits class for hash containers
	public:
	enum { // parameters for hash table
	bucket_size = 1 // 0 < bucket_size
	};
	hash_compare() = default;
	hash_compare(const _Pr& _Pred) noexcept(_STD is_nothrow_copy_constructible_v<_Pr>) : comp(_Pred) {}
	_NODISCARD size_t operator()(const _Kty& _Keyval) const noexcept(noexcept(hash_value(_Keyval))) {
	long _Quot = static_cast<long>(hash_value(_Keyval) & LONG_MAX); // TRANSITION, ADL?
	ldiv_t _Qrem = _CSTD ldiv(_Quot, 127773);
	_Qrem.rem = 16807 * _Qrem.rem - 2836 * _Qrem.quot;
	if (_Qrem.rem < 0) {
	_Qrem.rem += LONG_MAX;
	}
	return static_cast<size_t>(_Qrem.rem);
	}
	_NODISCARD bool operator()(const _Kty& _Keyval1, const _Kty& _Keyval2) const
	noexcept(noexcept(comp(_Keyval1, _Keyval2))) {
	// test if _Keyval1 ordered before _Keyval2
	return comp(_Keyval1, _Keyval2);
	}
	_Pr comp{}; // the comparator object
	};

So we don't visualize [hash_function] and [key_eq], we could visualize [comp] but it doesn't seem useful...

[StephanTLavavej]

No change requested: In theory, comp could be a function pointer worth visualizing. However, it seems likely that it would have to be paired with an ADL-customized hash_value and that seems quite rare (given the poorly-documented nature of this non-Standard extension). I'm okay with this as-is.

[StephanTLavavej]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[StephanTLavavej]

Thanks for finding and fixing this visualizer bug - hash_set may be deprecated, but we should still visualize it properly! 🎉 🐈 👁️