On Fri, 18 Apr 2025, 12:55 Tomasz Kamiński, <[email protected]> wrote:
> This implements part of LWG4223 that adjust the deduction guides for maps
> types
> (map, unordered_map, flat_map and non-unique equivalent) from "range",
> such that
> referience and cv qualification are stripped from the element of the
> pair-like
> value_type.
>
> In combination with r15-8296-gd50171bc07006d, the LWG4223 is fully
> implemented now.
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/ranges_base.h (__detail::__range_key_type):
> Replace remove_const_t with remove_cvref_t.
> (__detail::__range_mapped_type): Apply remove_cvref_t.
> * include/bits/stl_iterator.h: (__detail::__iter_key_t):
> Replace remove_const_t with __remove_cvref_t.
> (__detail::__iter_val_t): Apply __remove_cvref_t.
> * testsuite/23_containers/flat_map/1.cc: New tests.
> * testsuite/23_containers/flat_multimap/1.cc: New tests.
> * testsuite/23_containers/map/cons/deduction.cc: New tests.
> * testsuite/23_containers/map/cons/from_range.cc: New tests.
> * testsuite/23_containers/multimap/cons/deduction.cc: New tests.
> * testsuite/23_containers/multimap/cons/from_range.cc: New tests.
> * testsuite/23_containers/unordered_map/cons/deduction.cc: New
> tests.
> * testsuite/23_containers/unordered_map/cons/from_range.cc: New
> tests.
> * testsuite/23_containers/unordered_multimap/cons/deduction.cc:
> New tests.
> * testsuite/23_containers/unordered_multimap/cons/from_range.cc:
> New tests.
> ---
> Desipite there being some discussion about this on reflector, I think we
> should go ahead with this, to avoid creating maps of references/const
> types.
> As we are at the begining of development of 16, this seems like a good
> time
> to do it.
> OK for trunk?
>
OK for trunk.
>
> libstdc++-v3/include/bits/ranges_base.h | 4 +-
> libstdc++-v3/include/bits/stl_iterator.h | 11 +--
> .../testsuite/23_containers/flat_map/1.cc | 21 +++---
> .../23_containers/flat_multimap/1.cc | 21 +++---
> .../23_containers/map/cons/deduction.cc | 46 +++++++++++++
> .../23_containers/map/cons/from_range.cc | 8 +--
> .../23_containers/multimap/cons/deduction.cc | 46 +++++++++++++
> .../23_containers/multimap/cons/from_range.cc | 8 +--
> .../unordered_map/cons/deduction.cc | 69 +++++++++++++++++++
> .../unordered_map/cons/from_range.cc | 10 ++-
> .../unordered_multimap/cons/deduction.cc | 69 +++++++++++++++++++
> .../unordered_multimap/cons/from_range.cc | 10 +--
> 12 files changed, 279 insertions(+), 44 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/ranges_base.h
> b/libstdc++-v3/include/bits/ranges_base.h
> index 488907da446..dde16498856 100644
> --- a/libstdc++-v3/include/bits/ranges_base.h
> +++ b/libstdc++-v3/include/bits/ranges_base.h
> @@ -1103,11 +1103,11 @@ namespace __detail
> // 4223. Deduction guides for maps are mishandling tuples and references
> template<ranges::input_range _Range>
> using __range_key_type
> - = remove_const_t<tuple_element_t<0, ranges::range_value_t<_Range>>>;
> + = remove_cvref_t<tuple_element_t<0, ranges::range_value_t<_Range>>>;
>
> template<ranges::input_range _Range>
> using __range_mapped_type
> - = tuple_element_t<1, ranges::range_value_t<_Range>>;
> + = remove_cvref_t<tuple_element_t<1, ranges::range_value_t<_Range>>>;
>
> // The allocator's value_type for map-like containers.
> template<ranges::input_range _Range>
> diff --git a/libstdc++-v3/include/bits/stl_iterator.h
> b/libstdc++-v3/include/bits/stl_iterator.h
> index 9203a66b2ff..bed72955d0c 100644
> --- a/libstdc++-v3/include/bits/stl_iterator.h
> +++ b/libstdc++-v3/include/bits/stl_iterator.h
> @@ -3086,8 +3086,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> #if __cpp_deduction_guides >= 201606
> // These helper traits are used for deduction guides
> // of associative containers.
> +
> + // _GLIBCXX_RESOLVE_LIB_DEFECTS
> + // 4223. Deduction guides for maps are mishandling tuples and references
> template<typename _InputIterator>
> - using __iter_key_t = remove_const_t<
> + using __iter_key_t = __remove_cvref_t<
> #ifdef __glibcxx_tuple_like // >= C++23
> tuple_element_t<0, typename
> iterator_traits<_InputIterator>::value_type>>;
> #else
> @@ -3095,11 +3098,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> #endif
>
> template<typename _InputIterator>
> - using __iter_val_t
> + using __iter_val_t = __remove_cvref_t<
> #ifdef __glibcxx_tuple_like // >= C++23
> - = tuple_element_t<1, typename
> iterator_traits<_InputIterator>::value_type>;
> + tuple_element_t<1, typename
> iterator_traits<_InputIterator>::value_type>>;
> #else
> - = typename iterator_traits<_InputIterator>::value_type::second_type;
> + typename iterator_traits<_InputIterator>::value_type::second_type>;
> #endif
>
> template<typename _T1, typename _T2>
> diff --git a/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> b/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> index d9d88c4df6e..6105a2865c9 100644
> --- a/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> +++ b/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> @@ -55,16 +55,17 @@ test_deduction_guide()
> std::vector<long, __gnu_test::SimpleAllocator<long>>,
> std::vector<float,
> __gnu_test::SimpleAllocator<float>>>>);
>
> - // LWG4223: deduces flat_map<long, float const>, which in turn
> instantiates
> - // std::vector<cosnt float> that is ill-formed.
> - // __gnu_test::test_input_range<std::pair<const long, const float>>
> r2(0, 0);
> - // std::flat_map it5(r2.begin(), r2.begin());
> - // std::flat_map fr5(std::from_range, r2);
> -
> - // LWG4223: deduces flat_map<const long&, float&>
> - //__gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> - // std::flat_map it6(r3.begin(), r3.begin());
> - // std::flat_map fr6(std::from_range, r3);
> + __gnu_test::test_input_range<std::pair<const long, const float>> r2(0,
> 0);
> + std::flat_map it5(r2.begin(), r2.begin());
> + static_assert(std::is_same_v<decltype(it5), std::flat_map<long,
> float>>);
> + std::flat_map fr5(std::from_range, r2);
> + static_assert(std::is_same_v<decltype(fr5), std::flat_map<long,
> float>>);
> +
> + __gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> + std::flat_map it6(r3.begin(), r3.begin());
> + static_assert(std::is_same_v<decltype(it6), std::flat_map<long,
> float>>);
> + std::flat_map fr6(std::from_range, r3);
> + static_assert(std::is_same_v<decltype(fr6), std::flat_map<long,
> float>>);
>
> __gnu_test::test_input_range<std::tuple<long, float>> r4(0, 0);
> std::flat_map it7(r4.begin(), r4.begin());
> diff --git a/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> b/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> index ff180bf1bdf..ac8b0e0d7d9 100644
> --- a/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> +++ b/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> @@ -53,16 +53,17 @@ test_deduction_guide()
> std::vector<long, __gnu_test::SimpleAllocator<long>>,
> std::vector<float,
> __gnu_test::SimpleAllocator<float>>>>);
>
> - // LWG4223: deduces flat_multimap<long, float const>, which in turn
> instantiates
> - // std::vector<cosnt float> that is ill-formed.
> - // __gnu_test::test_input_range<std::pair<const long, const float>>
> r2(0, 0);
> - // std::flat_multimap it5(r2.begin(), r2.begin());
> - // std::flat_multimap fr5(std::from_range, r2);
> -
> - // LWG4223: deduces flat_multimap<const long&, float&>
> - //__gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> - // std::flat_multimap it6(r3.begin(), r3.begin());
> - // std::flat_multimap fr6(std::from_range, r3);
> + __gnu_test::test_input_range<std::pair<const long, const float>> r2(0,
> 0);
> + std::flat_multimap it5(r2.begin(), r2.begin());
> + static_assert(std::is_same_v<decltype(it5), std::flat_multimap<long,
> float>>);
> + std::flat_multimap fr5(std::from_range, r2);
> + static_assert(std::is_same_v<decltype(fr5), std::flat_multimap<long,
> float>>);
> +
> + __gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> + std::flat_multimap it6(r3.begin(), r3.begin());
> + static_assert(std::is_same_v<decltype(it6), std::flat_multimap<long,
> float>>);
> + std::flat_multimap fr6(std::from_range, r3);
> + static_assert(std::is_same_v<decltype(fr6), std::flat_multimap<long,
> float>>);
>
> __gnu_test::test_input_range<std::tuple<long, float>> r4(0, 0);
> std::flat_multimap it7(r4.begin(), r4.begin());
> diff --git a/libstdc++-v3/testsuite/23_containers/map/cons/deduction.cc
> b/libstdc++-v3/testsuite/23_containers/map/cons/deduction.cc
> index f8e6e6e8b99..194bff5bf78 100644
> --- a/libstdc++-v3/testsuite/23_containers/map/cons/deduction.cc
> +++ b/libstdc++-v3/testsuite/23_containers/map/cons/deduction.cc
> @@ -258,3 +258,49 @@ test_p1518r2()
> std::map s2(std::move(m), p);
> check_type<Map>(s2);
> }
> +
> +struct MyPred
> +{
> + template<typename T, typename U>
> + bool operator()(T const&, U const&) const;
> +};
> +
> +template<typename K, typename V>
> +constexpr bool test_lwg4223()
> +{
> + using KD = std::remove_cvref_t<K>;
> + using VD = std::remove_cvref_t<V>;
> + using Alloc = __gnu_test::SimpleAllocator<std::pair<const KD, VD>>;
> +
> + std::initializer_list<std::pair<K, V>> il = {};
> + Alloc a;
> + MyPred p;
> +
> + // The remove_cvref_t is not applied here.
> + // static_assert(std::is_same_v<
> + // decltype(std::map(il)),
> + // std::map<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::map(il.begin(), il.end())),
> + std::map<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::map(il.begin(), il.end(), p)),
> + std::map<KD, VD, MyPred>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::map(il.begin(), il.end(), a)),
> + std::map<KD, VD, std::less<KD>, Alloc>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::map(il.begin(), il.end(), p, a)),
> + std::map<KD, VD, MyPred, Alloc>>);
> +
> + return true;
> +}
> +
> +static_assert(test_lwg4223<const int, const float>());
> +static_assert(test_lwg4223<int&, float&>());
> +static_assert(test_lwg4223<int&&, float&&>());
> +static_assert(test_lwg4223<const int&, const float&>());
> diff --git a/libstdc++-v3/testsuite/23_containers/map/cons/from_range.cc
> b/libstdc++-v3/testsuite/23_containers/map/cons/from_range.cc
> index 9935f44aa0f..3a9fede0434 100644
> --- a/libstdc++-v3/testsuite/23_containers/map/cons/from_range.cc
> +++ b/libstdc++-v3/testsuite/23_containers/map/cons/from_range.cc
> @@ -43,11 +43,11 @@ test_deduction_guide()
>
> __gnu_test::test_input_range<std::pair<const long, const float>> r2(0,
> 0);
> std::map m5(std::from_range, r2);
> - static_assert(std::is_same_v<decltype(m5), std::map<long, const
> float>>);
> + static_assert(std::is_same_v<decltype(m5), std::map<long, float>>);
>
> - // LWG4223: deduces map<const long&, float&>
> - //__gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> - // std::map m6(std::from_range, r3);
> + __gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> + std::map m6(std::from_range, r3);
> + static_assert(std::is_same_v<decltype(m6), std::map<long, float>>);
>
> __gnu_test::test_input_range<std::tuple<long, float>> r4(0, 0);
> std::map m7(std::from_range, r4);
> diff --git
> a/libstdc++-v3/testsuite/23_containers/multimap/cons/deduction.cc
> b/libstdc++-v3/testsuite/23_containers/multimap/cons/deduction.cc
> index f0699e2eefc..84754f3f561 100644
> --- a/libstdc++-v3/testsuite/23_containers/multimap/cons/deduction.cc
> +++ b/libstdc++-v3/testsuite/23_containers/multimap/cons/deduction.cc
> @@ -210,3 +210,49 @@ test_p1518r2()
> std::multimap s2(std::move(m), p);
> check_type<MMap>(s2);
> }
> +
> +struct MyPred
> +{
> + template<typename T, typename U>
> + bool operator()(T const&, U const&) const;
> +};
> +
> +template<typename K, typename V>
> +constexpr bool test_lwg4223()
> +{
> + using KD = std::remove_cvref_t<K>;
> + using VD = std::remove_cvref_t<V>;
> + using Alloc = __gnu_test::SimpleAllocator<std::pair<const KD, VD>>;
> +
> + std::initializer_list<std::pair<K, V>> il = {};
> + Alloc a;
> + MyPred p;
> +
> + // The remove_cvref_t is not applied here.
> + // static_assert(std::is_same_v<
> + // decltype(std::multimap(il)),
> + // std::multimap<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::multimap(il.begin(), il.end())),
> + std::multimap<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::multimap(il.begin(), il.end(), p)),
> + std::multimap<KD, VD, MyPred>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::multimap(il.begin(), il.end(), a)),
> + std::multimap<KD, VD, std::less<KD>, Alloc>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::multimap(il.begin(), il.end(), p, a)),
> + std::multimap<KD, VD, MyPred, Alloc>>);
> +
> + return true;
> +}
> +
> +static_assert(test_lwg4223<const int, const float>());
> +static_assert(test_lwg4223<int&, float&>());
> +static_assert(test_lwg4223<int&&, float&&>());
> +static_assert(test_lwg4223<const int&, const float&>());
> diff --git
> a/libstdc++-v3/testsuite/23_containers/multimap/cons/from_range.cc
> b/libstdc++-v3/testsuite/23_containers/multimap/cons/from_range.cc
> index 4a8ea9fec7d..5907bab9878 100644
> --- a/libstdc++-v3/testsuite/23_containers/multimap/cons/from_range.cc
> +++ b/libstdc++-v3/testsuite/23_containers/multimap/cons/from_range.cc
> @@ -43,11 +43,11 @@ test_deduction_guide()
>
> __gnu_test::test_input_range<std::pair<const long, const float>> r2(0,
> 0);
> std::multimap m5(std::from_range, r2);
> - static_assert(std::is_same_v<decltype(m5), std::multimap<long, const
> float>>);
> + static_assert(std::is_same_v<decltype(m5), std::multimap<long, float>>);
>
> - // LWG4223: deduces multimap<const long&, float&>
> - //__gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> - // std::multimap m6(std::from_range, r3);
> + __gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> + std::multimap m6(std::from_range, r3);
> + static_assert(std::is_same_v<decltype(m6), std::multimap<long, float>>);
>
> __gnu_test::test_input_range<std::tuple<long, float>> r4(0, 0);
> std::multimap m7(std::from_range, r4);
> diff --git
> a/libstdc++-v3/testsuite/23_containers/unordered_map/cons/deduction.cc
> b/libstdc++-v3/testsuite/23_containers/unordered_map/cons/deduction.cc
> index 8b69af896a2..e806de2045c 100644
> --- a/libstdc++-v3/testsuite/23_containers/unordered_map/cons/deduction.cc
> +++ b/libstdc++-v3/testsuite/23_containers/unordered_map/cons/deduction.cc
> @@ -162,3 +162,72 @@ test_p1518r2()
> std::unordered_map s2(std::move(m), p);
> check_type<UMap>(s2);
> }
> +
> +struct MyHash
> +{
> + template<typename T>
> + std::size_t operator()(T const&) const;
> +};
> +
> +struct MyPred
> +{
> + template<typename T, typename U>
> + bool operator()(T const&, U const&) const;
> +};
> +
> +template<typename K, typename V>
> +constexpr bool test_lwg4223()
> +{
> + using KD = std::remove_cvref_t<K>;
> + using VD = std::remove_cvref_t<V>;
> + using Alloc = __gnu_test::SimpleAllocator<std::pair<const KD, VD>>;
> +
> + std::initializer_list<std::pair<K, V>> il = {};
> + Alloc a;
> + MyHash h;
> + MyPred p;
> +
> + // The remove_cvref_t is not applied here.
> + // static_assert(std::is_same_v<
> + // decltype(std::unordered_map(il)),
> + // std::unordered_map<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_map(il.begin(), il.end())),
> + std::unordered_map<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_map(il.begin(), il.end(), 0)),
> + std::unordered_map<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_map(il.begin(), il.end(), 0, h)),
> + std::unordered_map<KD, VD, MyHash>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_map(il.begin(), il.end(), 0, h, p)),
> + std::unordered_map<KD, VD, MyHash, MyPred>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_map(il.begin(), il.end(), a)),
> + std::unordered_map<KD, VD, std::hash<KD>, std::equal_to<KD>, Alloc>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_map(il.begin(), il.end(), 0, a)),
> + std::unordered_map<KD, VD, std::hash<KD>, std::equal_to<KD>, Alloc>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_map(il.begin(), il.end(), 0, h, a)),
> + std::unordered_map<KD, VD, MyHash, std::equal_to<KD>, Alloc>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_map(il.begin(), il.end(), 0, h, p, a)),
> + std::unordered_map<KD, VD, MyHash, MyPred, Alloc>>);
> +
> + return true;
> +}
> +
> +static_assert(test_lwg4223<const int, const float>());
> +static_assert(test_lwg4223<int&, float&>());
> +static_assert(test_lwg4223<int&&, float&&>());
> +static_assert(test_lwg4223<const int&, const float&>());
> diff --git
> a/libstdc++-v3/testsuite/23_containers/unordered_map/cons/from_range.cc
> b/libstdc++-v3/testsuite/23_containers/unordered_map/cons/from_range.cc
> index 36efc2de5a3..04479a5e54d 100644
> --- a/libstdc++-v3/testsuite/23_containers/unordered_map/cons/from_range.cc
> +++ b/libstdc++-v3/testsuite/23_containers/unordered_map/cons/from_range.cc
> @@ -78,13 +78,11 @@ test_deduction_guide()
>
> __gnu_test::test_input_range<std::pair<const long, const float>> r2(0,
> 0);
> std::unordered_map m9(std::from_range, r2);
> - static_assert(std::is_same_v<
> - decltype(m9),
> - std::unordered_map<long, const float>>);
> + static_assert(std::is_same_v<decltype(m9), std::unordered_map<long,
> float>>);
>
> - // LWG4223: deduces map<const long&, float&>
> - // __gnu_test::test_input_range<std::pair<const long&, float&>> r3(0,
> 0);
> - // std::unordered_map m10(std::from_range, r3);
> + __gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> + std::unordered_map m10(std::from_range, r3);
> + static_assert(std::is_same_v<decltype(m10), std::unordered_map<long,
> float>>);
>
> __gnu_test::test_input_range<std::tuple<long, float>> r4(0, 0);
> std::unordered_map m11(std::from_range, r4);
> diff --git
> a/libstdc++-v3/testsuite/23_containers/unordered_multimap/cons/deduction.cc
> b/libstdc++-v3/testsuite/23_containers/unordered_multimap/cons/deduction.cc
> index e7e535b527a..786e5030bb2 100644
> ---
> a/libstdc++-v3/testsuite/23_containers/unordered_multimap/cons/deduction.cc
> +++
> b/libstdc++-v3/testsuite/23_containers/unordered_multimap/cons/deduction.cc
> @@ -171,3 +171,72 @@ test_p1518r2()
> std::unordered_multimap s2(std::move(m), p);
> check_type<UMMap>(s2);
> }
> +
> +struct MyHash
> +{
> + template<typename T>
> + std::size_t operator()(T const&) const;
> +};
> +
> +struct MyPred
> +{
> + template<typename T, typename U>
> + bool operator()(T const&, U const&) const;
> +};
> +
> +template<typename K, typename V>
> +constexpr bool test_lwg4223()
> +{
> + using KD = std::remove_cvref_t<K>;
> + using VD = std::remove_cvref_t<V>;
> + using Alloc = __gnu_test::SimpleAllocator<std::pair<const KD, VD>>;
> +
> + std::initializer_list<std::pair<K, V>> il = {};
> + Alloc a;
> + MyHash h;
> + MyPred p;
> +
> + // The remove_cvref_t is not applied here.
> + // static_assert(std::is_same_v<
> + // decltype(std::unordered_multimap(il)),
> + // std::unordered_multimap<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_multimap(il.begin(), il.end())),
> + std::unordered_multimap<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_multimap(il.begin(), il.end(), 0)),
> + std::unordered_multimap<KD, VD>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_multimap(il.begin(), il.end(), 0, h)),
> + std::unordered_multimap<KD, VD, MyHash>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_multimap(il.begin(), il.end(), 0, h, p)),
> + std::unordered_multimap<KD, VD, MyHash, MyPred>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_multimap(il.begin(), il.end(), a)),
> + std::unordered_multimap<KD, VD, std::hash<KD>, std::equal_to<KD>,
> Alloc>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_multimap(il.begin(), il.end(), 0, a)),
> + std::unordered_multimap<KD, VD, std::hash<KD>, std::equal_to<KD>,
> Alloc>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_multimap(il.begin(), il.end(), 0, h, a)),
> + std::unordered_multimap<KD, VD, MyHash, std::equal_to<KD>, Alloc>>);
> +
> + static_assert(std::is_same_v<
> + decltype(std::unordered_multimap(il.begin(), il.end(), 0, h, p, a)),
> + std::unordered_multimap<KD, VD, MyHash, MyPred, Alloc>>);
> +
> + return true;
> +}
> +
> +static_assert(test_lwg4223<const int, const float>());
> +static_assert(test_lwg4223<int&, float&>());
> +static_assert(test_lwg4223<int&&, float&&>());
> +static_assert(test_lwg4223<const int&, const float&>());
> diff --git
> a/libstdc++-v3/testsuite/23_containers/unordered_multimap/cons/from_range.cc
> b/libstdc++-v3/testsuite/23_containers/unordered_multimap/cons/from_range.cc
> index b551df49f3e..4567bd8aa91 100644
> ---
> a/libstdc++-v3/testsuite/23_containers/unordered_multimap/cons/from_range.cc
> +++
> b/libstdc++-v3/testsuite/23_containers/unordered_multimap/cons/from_range.cc
> @@ -86,11 +86,13 @@ test_deduction_guide()
> std::unordered_multimap m9(std::from_range, r2);
> static_assert(std::is_same_v<
> decltype(m9),
> - std::unordered_multimap<long, const float>>);
> + std::unordered_multimap<long, float>>);
>
> - // LWG4223: deduces map<const long&, float&>
> - // __gnu_test::test_input_range<std::pair<const long&, float&>> r3(0,
> 0);
> - // std::unordered_multimap m10(std::from_range, r3);
> + __gnu_test::test_input_range<std::pair<const long&, float&>> r3(0, 0);
> + std::unordered_multimap m10(std::from_range, r3);
> + static_assert(std::is_same_v<
> + decltype(m10),
> + std::unordered_multimap<long, float>>);
>
> __gnu_test::test_input_range<std::tuple<long, float>> r4(0, 0);
> std::unordered_multimap m11(std::from_range, r4);
> --
> 2.49.0
>
>
