P1518R2 Stop Overconstraining Allocators In Container Deduction Guides

stl/inc/deque

@@ -11,6 +11,7 @@
 #include <xmemory>
 
 #if _HAS_CXX17
+#include <type_traits>
 #include <xpolymorphic_allocator.h>
 #endif // _HAS_CXX17
 
@@ -652,7 +653,12 @@ public:
         _Proxy._Release();
     }
 
-    deque(const deque& _Right, const _Alloc& _Al) : _Mypair(_One_then_variadic_args_t{}, _Al) {
+#if _HAS_CXX17
+    deque(const deque& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    deque(const deque& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        : _Mypair(_One_then_variadic_args_t{}, _Al) {
         _Alproxy_ty _Alproxy(_Getal());
         _Container_proxy_ptr12<_Alproxy_ty> _Proxy(_Alproxy, _Get_data());
         _Construct(_Right._Unchecked_begin(), _Right._Unchecked_end());
@@ -701,7 +707,12 @@ public:
         _Take_contents(_Right);
     }
 
-    deque(deque&& _Right, const _Alloc& _Al) : _Mypair(_One_then_variadic_args_t{}, _Al) {
+#if _HAS_CXX17
+    deque(deque&& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    deque(deque&& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        : _Mypair(_One_then_variadic_args_t{}, _Al) {
         _Alproxy_ty _Alproxy(_Getal());
         if constexpr (!_Alty_traits::is_always_equal::value) {
             if (_Getal() != _Right._Getal()) {

stl/inc/forward_list

@@ -11,6 +11,7 @@
 #include <xmemory>
 
 #if _HAS_CXX17
+#include <type_traits>
 #include <xpolymorphic_allocator.h>
 #endif // _HAS_CXX17
 
@@ -587,7 +588,12 @@ public:
         _Insert_op._Attach_after(_Mypair._Myval2._Before_head());
     }
 
-    forward_list(const forward_list& _Right, const _Alloc& _Al) : _Mypair(_One_then_variadic_args_t{}, _Al) {
+#if _HAS_CXX17
+    forward_list(const forward_list& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    forward_list(const forward_list& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        : _Mypair(_One_then_variadic_args_t{}, _Al) {
         _Flist_insert_after_op2<_Alnode> _Insert_op(_Getal());
         _Insert_op._Append_range_unchecked(_Right._Unchecked_begin(), _Right._Unchecked_end());
         _Alloc_proxy();
@@ -618,8 +624,12 @@ public:
         _Take_head(_Right);
     }
 
-    forward_list(forward_list&& _Right, const _Alloc& _Al) noexcept(
-        _Alnode_traits::is_always_equal::value) // strengthened
+#if _HAS_CXX17
+    forward_list(forward_list&& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    forward_list(forward_list&& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        noexcept(_Alnode_traits::is_always_equal::value) // strengthened
         : _Mypair(_One_then_variadic_args_t{}, _Al) {
         if constexpr (!_Alty_traits::is_always_equal::value) {
             if (_Getal() != _Right._Getal()) {

stl/inc/list

@@ -11,6 +11,7 @@
 #include <xmemory>
 
 #if _HAS_CXX17
+#include <type_traits>
 #include <xpolymorphic_allocator.h>
 #endif // _HAS_CXX17
 
@@ -873,7 +874,12 @@ public:
         _Construct_range_unchecked(_Right._Unchecked_begin(), _Right._Unchecked_end());
     }
 
-    list(const list& _Right, const _Alloc& _Al) : _Mypair(_One_then_variadic_args_t{}, _Al) {
+#if _HAS_CXX17
+    list(const list& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    list(const list& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        : _Mypair(_One_then_variadic_args_t{}, _Al) {
         _Construct_range_unchecked(_Right._Unchecked_begin(), _Right._Unchecked_end());
     }
 
@@ -894,7 +900,12 @@ public:
         _Swap_val(_Right);
     }
 
-    list(list&& _Right, const _Alloc& _Al) : _Mypair(_One_then_variadic_args_t{}, _Al) {
+#if _HAS_CXX17
+    list(list&& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    list(list&& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        : _Mypair(_One_then_variadic_args_t{}, _Al) {
         if constexpr (!_Alnode_traits::is_always_equal::value) {
             if (_Getal() != _Right._Getal()) {
                 _Construct_range_unchecked(_STD make_move_iterator(_Right._Unchecked_begin()),

stl/inc/queue

@@ -121,9 +121,7 @@ template <class _Container, enable_if_t<!_Is_allocator<_Container>::value, int>
 queue(_Container) -> queue<typename _Container::value_type, _Container>;
 
 template <class _Container, class _Alloc,
-    enable_if_t<
-        conjunction_v<negation<_Is_allocator<_Container>>, _Is_allocator<_Alloc>, uses_allocator<_Container, _Alloc>>,
-        int> = 0>
+    enable_if_t<conjunction_v<negation<_Is_allocator<_Container>>, uses_allocator<_Container, _Alloc>>, int> = 0>
 queue(_Container, _Alloc) -> queue<typename _Container::value_type, _Container>;
 #endif // _HAS_CXX17
 
@@ -307,7 +305,7 @@ priority_queue(_Iter, _Iter, _Pr = _Pr(), _Container = _Container())
     -> priority_queue<_Iter_value_t<_Iter>, _Container, _Pr>;
 
 template <class _Pr, class _Container, class _Alloc,
-    enable_if_t<conjunction_v<negation<_Is_allocator<_Pr>>, negation<_Is_allocator<_Container>>, _Is_allocator<_Alloc>,
+    enable_if_t<conjunction_v<negation<_Is_allocator<_Pr>>, negation<_Is_allocator<_Container>>,
                     uses_allocator<_Container, _Alloc>>,
         int> = 0>
 priority_queue(_Pr, _Container, _Alloc) -> priority_queue<typename _Container::value_type, _Container, _Pr>;

stl/inc/stack

@@ -111,9 +111,7 @@ template <class _Container, enable_if_t<!_Is_allocator<_Container>::value, int>
 stack(_Container) -> stack<typename _Container::value_type, _Container>;
 
 template <class _Container, class _Alloc,
-    enable_if_t<
-        conjunction_v<negation<_Is_allocator<_Container>>, _Is_allocator<_Alloc>, uses_allocator<_Container, _Alloc>>,
-        int> = 0>
+    enable_if_t<conjunction_v<negation<_Is_allocator<_Container>>, uses_allocator<_Container, _Alloc>>, int> = 0>
 stack(_Container, _Alloc) -> stack<typename _Container::value_type, _Container>;
 #endif // _HAS_CXX17
 

stl/inc/vector

@@ -11,6 +11,7 @@
 #include <xmemory>
 
 #if _HAS_CXX17
+#include <type_traits>
 #include <xpolymorphic_allocator.h>
 #endif // _HAS_CXX17
 
@@ -527,7 +528,12 @@ public:
         _Construct_n(_Count, _Right_data._Myfirst, _Right_data._Mylast);
     }
 
-    _CONSTEXPR20_CONTAINER vector(const vector& _Right, const _Alloc& _Al) : _Mypair(_One_then_variadic_args_t{}, _Al) {
+#if _HAS_CXX17
+    _CONSTEXPR20_CONTAINER vector(const vector& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    _CONSTEXPR20_CONTAINER vector(const vector& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        : _Mypair(_One_then_variadic_args_t{}, _Al) {
         const auto& _Right_data = _Right._Mypair._Myval2;
         const auto _Count       = static_cast<size_type>(_Right_data._Mylast - _Right_data._Myfirst);
         _Construct_n(_Count, _Right_data._Myfirst, _Right_data._Mylast);
@@ -542,8 +548,12 @@ public:
         _Mypair._Myval2._Swap_proxy_and_iterators(_Right._Mypair._Myval2);
     }
 
-    _CONSTEXPR20_CONTAINER vector(vector&& _Right, const _Alloc& _Al_) noexcept(
-        _Alty_traits::is_always_equal::value) // strengthened
+#if _HAS_CXX17
+    _CONSTEXPR20_CONTAINER vector(vector&& _Right, const _Identity_t<_Alloc>& _Al_)
+#else
+    _CONSTEXPR20_CONTAINER vector(vector&& _Right, const _Alloc& _Al_)
+#endif // _HAS_CXX17
+        noexcept(_Alty_traits::is_always_equal::value) // strengthened
         : _Mypair(_One_then_variadic_args_t{}, _Al_) {
         _Alty& _Al        = _Getal();
         auto&& _Alproxy   = _GET_PROXY_ALLOCATOR(_Alty, _Al);
@@ -2487,7 +2497,13 @@ public:
 
     _CONSTEXPR20_CONTAINER vector(const vector& _Right) : _Mybase(_Right) {}
 
-    _CONSTEXPR20_CONTAINER vector(const vector& _Right, const _Alloc& _Al) : _Mybase(_Right, _Al) {}
+#if _HAS_CXX17
+    _CONSTEXPR20_CONTAINER vector(const vector& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    _CONSTEXPR20_CONTAINER vector(const vector& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        : _Mybase(_Right, _Al) {
+    }
 
     template <class _Iter, enable_if_t<_Is_iterator_v<_Iter>, int> = 0>
     _CONSTEXPR20_CONTAINER vector(_Iter _First, _Iter _Last, const _Alloc& _Al = _Alloc()) : _Mybase(_Al) {
@@ -2504,8 +2520,12 @@ public:
         this->_Swap_proxy_and_iterators(_Right);
     }
 
-    _CONSTEXPR20_CONTAINER vector(vector&& _Right, const _Alloc& _Al) noexcept(
-        is_nothrow_constructible_v<_Mybase, _Mybase, const _Alloc&>)
+#if _HAS_CXX17
+    _CONSTEXPR20_CONTAINER vector(vector&& _Right, const _Identity_t<_Alloc>& _Al)
+#else
+    _CONSTEXPR20_CONTAINER vector(vector&& _Right, const _Alloc& _Al)
+#endif // _HAS_CXX17
+        noexcept(is_nothrow_constructible_v<_Mybase, _Mybase, const _Alloc&>)
         : _Mybase(_STD move(_Right), _Al) {
         if constexpr (!_Alvbase_traits::is_always_equal::value) {
             if (this->_Getal() != _Right._Getal()) {

stl/inc/yvals_core.h

@@ -111,6 +111,7 @@
 // P0858R0 Constexpr Iterator Requirements
 // P1065R2 constexpr INVOKE
 //     (the std::invoke function only; other components like bind and reference_wrapper are C++20 only)
+// P1518R2 Stop Overconstraining Allocators In Container Deduction Guides
 // P2162R2 Inheriting From variant
 
 // _HAS_CXX17 indirectly controls:

tests/std/test.lst

@@ -417,6 +417,7 @@ tests\P1165R1_consistently_propagating_stateful_allocators
 tests\P1208R6_source_location
 tests\P1423R3_char8_t_remediation
 tests\P1502R1_standard_library_header_units
+tests\P1518R2_stop_overconstraining_allocators
 tests\P1614R2_spaceship
 tests\P1645R1_constexpr_numeric
 tests\P1682R3_to_underlying

tests/std/tests/P1518R2_stop_overconstraining_allocators/env.lst

@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_17_matrix.lst

tests/std/tests/P1518R2_stop_overconstraining_allocators/test.compile.pass.cpp

@@ -0,0 +1,107 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <deque>
+#include <forward_list>
+#include <list>
+#include <map>
+#include <memory_resource>
+#include <queue>
+#include <set>
+#include <stack>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+using namespace std;
+
+extern pmr::monotonic_buffer_resource mr;
+
+template <template <class...> class Ctr>
+struct SfinaeTester {
+    template <class... Args>
+    static auto f(int, Args&&... args) -> decltype(Ctr(static_cast<Args&&>(args)...)) {
+        return Ctr(static_cast<Args&&>(args)...);
+    }
+    template <class... Args>
+    static void f(long, Args&&... /*args*/) {}
+
+    template <class... Args>
+    static auto test(Args&&... args) {
+        return f(0, static_cast<Args&&>(args)...);
+    }
+};
+
+auto test_deque(pmr::deque<int>& px) {
+    auto x = SfinaeTester<deque>::test(px, &mr);
+}
+
+auto test_forward_list(pmr::forward_list<int>& px) {
+    auto x = SfinaeTester<forward_list>::test(px, &mr);
+}
+
+auto test_list(pmr::list<int>& px) {
+    auto x = SfinaeTester<list>::test(px, &mr);
+}
+
+auto test_vector(pmr::vector<int>& px) {
+    auto x = SfinaeTester<vector>::test(px, &mr);
+}
+
+auto test_map(pmr::map<int, int>& px) {
+    auto x = SfinaeTester<map>::test(px, &mr);
+}
+
+auto test_multimap(pmr::multimap<int, int>& px) {
+    auto x = SfinaeTester<multimap>::test(px, &mr);
+}
+
+auto test_multiset(pmr::multiset<int>& px) {
+    auto x = SfinaeTester<multiset>::test(px, &mr);
+}
+
+auto test_set(pmr::set<int>& px) {
+    auto x = SfinaeTester<set>::test(px, &mr);
+}
+
+auto test_unordered_map(pmr::unordered_map<int, int>& px) {
+    auto x = SfinaeTester<unordered_map>::test(px, &mr);
+}
+
+auto test_unordered_multimap(pmr::unordered_multimap<int, int>& px) {
+    auto x = SfinaeTester<unordered_multimap>::test(px, &mr);
+}
+
+auto test_unordered_multiset(pmr::unordered_multiset<int>& px) {
+    auto x = SfinaeTester<unordered_multiset>::test(px, &mr);
+}
+
+auto test_unordered_set(pmr::unordered_set<int>& px) {
+    auto x = SfinaeTester<unordered_set>::test(px, &mr);
+}
+
+auto test_priority_queue1(priority_queue<int, pmr::vector<int>>& px) {
+    auto x = SfinaeTester<priority_queue>::test(px, &mr);
+}
+
+auto test_queue1(queue<int, pmr::deque<int>>& px) {
+    auto x = SfinaeTester<queue>::test(px, &mr);
+}
+
+auto test_stack1(stack<int, pmr::vector<int>>& px) {
+    auto x = SfinaeTester<stack>::test(px, &mr);
+}
+
+auto test_priority_queue2(less<int> comp, pmr::vector<int>& pc) {
+    auto x = SfinaeTester<priority_queue>::test(comp, pc, &mr);
+}
+
+auto test_queue2(pmr::deque<int>& pc) {
+    auto x = SfinaeTester<queue>::test(pc, &mr);
+}
+
+auto test_stack2(pmr::vector<int>& pc) {
+    auto x = SfinaeTester<stack>::test(pc, &mr);
+}
+
+int main() {} // COMPILE-ONLY