[libc++] P0433R2: test that deduction guides are properly SFINAEd away.

[var-const]

Summary

Deduction guides for containers should not participate in overload
resolution when called with certain incorrect types (e.g. when called
with a template argument in place of an InputIterator that doesn't
qualify as an input iterator). Similarly, class template argument
deduction should not select unique_ptr constructors that take a
a pointer.

The tests try out every possible incorrect parameter (but never more
than one incorrect parameter in the same invocation).

Also add deduction guides to the synopsis for associative and unordered
containers (this was accidentally omitted from D112510).

[var-const]

Uncomment working test

[var-const]

Missing includes

[ldionne]

Thanks a lot for the patch! I have some requests for changes but overall this is looking pretty good!

libcxx/docs/Status/Cxx17Papers.csv

97

The next release this gets in will be 14.0, not 13.0! 13.0 is the current latest release.

libcxx/include/__memory/allocator_traits.h

352–354

You can replace the link once you have a LWG issue number!

libcxx/include/map

229

Those should be marked as being new in // C++17. This applies elsewhere, so you might want to do a NFC patch that adjusts that in all the containers, or just fix it everywhere in this commit. I think both are reasonable, fixing everything right now is probably less churn so I'd go for that.

libcxx/include/set

477

I checked and this wasn't used anywhere -- that's why it's being removed right?

libcxx/test/std/containers/associative/set/set.cons/deduct.pass.cpp

190–191

This file is indented at 2 columns.

libcxx/test/std/containers/container.adaptors/priority.queue/priqueue.cons/deduct.pass.cpp

251–263

I don't feel like this list adds very much since you commented the individual test cases below (thanks a bunch for doing that BTW). Feel free to keep them if you want, that's just my .02.

273

This is never used, and that's why the GCC build is failing. Did you forget a test case?

libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/deduct.fail.cpp

9 ↗

(On Diff #383710)

Is there a reason why this one isn't based on SFINAE checks like the container tests?

libcxx/test/support/sfinaes_away.h

15–28 ↗

(On Diff #383710)

IMO this utility is a bit too narrow in usefulness to make it its own header, since it only works for checking that a class template's CTAD SFINAEs away. If this were for checking that a general expression SFINAEs away, then I'd be in favour of keeping it standalone.

I would suggest either moving it to deduction_guides_sfinae_checks.h or generalizing it.

[• Quuxplusone]

I've looked only at the new deque code, but my comments probably apply equally to all the containers.

libcxx/include/deque

1269

I don't believe this is needed. By the time we are instantiating the members of deque<T, allocator_type>, we are guaranteed that allocator_type is an Allocator type.

1572

FWIW, __iter_value_type<_InputIterator> means typename iterator_traits<_InputIterator>::value_type, which is ill-formed (SFINAE-friendly) unless _InputIterator is an iterator type. However, I guess what you're doing here is protecting against the possibility that _InputIterator could be an output iterator? ...But you have added no tests for that new behavior, AFAICT.

Please replace all your new tests with something simple that demonstrates the new behavior, e.g. https://godbolt.org/z/aKeh1fE9Y

template<class... Args>
auto deque_has_ctad_from(int, Args&&... args) -> decltype(std::deque(std::forward<Args>(args)...), true) { return true; }
template<class... Args>
bool deque_has_ctad_from(long, Args&&...) { return false; }

int main() {
    std::vector<int> v;
    auto out = std::back_inserter(v);
    assert(!deque_has_ctad_from(42, out, out));
}

libcxx/test/support/sfinaes_away.h

15–28 ↗

(On Diff #383710)

+1 and more so: I don't think this PR should add any new headers. Each "deduct.pass.cpp" should just introduce a four-line bool foo_has_ctad_from(42, args...) (for the appropriate container-name foo).

[ldionne]

libcxx/include/deque

1572

FWIW, the Standard does not request that we check for anything more than "an integral type is not an input iterator". I agree we should change the tests that currently pass a struct BadIter { }; to make them pass a using BadIter = some-output-iterator;. And we need to mark those as libc++ specific, since that's technically just our QOI.

libcxx/test/support/deduction_guides_sfinae_checks.h

58

Per our offline discussion, let's add a test where we pass an integer type as an iterator and watch it fail, and also a libc++ specific test that passes an output iterator.

Note that we can't add an integer type test to the sequence containers, because those won't SFINAE away (the sequence containers can deduce from FOO(size_type, value_type) when passed two integers).

libcxx/test/support/sfinaes_away.h

15–28 ↗

(On Diff #383710)

I disagree with that. I looked at the PR in a previous stage where the checks were duplicated, and there was *a lot* of code duplication. Since most of these requirements are specified in http://eel.is/c++draft/container.requirements.general, I think it makes sense to colocate the tests the way they are right now.

[var-const]

Address feedback

libcxx/include/__memory/allocator_traits.h

352–354

Done, thanks!

libcxx/include/deque

1269

Sorry, I actually had a comment about this but forgot to post it before sending the patch out for review. Unfortunately, both of these changes (not using __base here and using the newly-added __allocator_traits) are necessary -- without them, the compiler would attempt to instantiate allocator_traits with allocator_type, which would result in instantiation errors if the given allocator_type doesn't have value_type. This affects all sequential containers and leads to verbose errors when trying to deduce from a bad allocator rather than silently sfinae'ing away a bad invocation.

I can dig more into this if you feel it warrants investigation.

1572

For adding this check, my main motivation was to make the requirement explicit, and also to be consistent with other similar checks. It seems to me that the fact that __iter_value_type also SFINAEs away "bad" input iterators is arguably an implementation detail, or at the very least, it's not as obvious without knowing the implementation as an explicit check.

I changed the tests that deal with bad iterators to use output iterators and also, where possible, to use integral types. PTAL.

libcxx/include/map

229

Fixed everything in this patch.

libcxx/include/set

477

Sorry, I wrote a comment about it but forgot to post it. Yes, I was investigating a compiler error stemming from the instantiation of __base requested here and noticed that __node_holder appears unused, so it seemed reasonable to remove it. I can split it into a separate small patch if you prefer.

504

Without this change (which is used in map and multimap) certain incorrect invocations try to do instantiations that depend on _Compare, leading to verbose errors.

libcxx/test/std/containers/container.adaptors/priority.queue/priqueue.cons/deduct.pass.cpp

251–263

Yeah, I was on the fence about leaving these in -- removed now.

273

Thanks for spotting! Yes, looks like I missed 3 test cases.

libcxx/test/std/containers/container.adaptors/stack/stack.cons/deduct.pass.cpp

140

stack and queue have the same tests, but it didn't seem worthwhile to refactor them out in a separate function.

libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/deduct.fail.cpp

9 ↗

(On Diff #383710)

For containers, the requirement is for deduction guides to not participate in overload resolution, but for unique pointers, the requirement is that If class template argument deduction would select the function template corresponding to this constructor, then the program is ill-formed. I interpreted ill-formed as "resulting in a hard error" -- please let me know if this is incorrect.

libcxx/test/support/deduction_guides_sfinae_checks.h

23

Please let me know if you'd prefer shorter names for these functions.

libcxx/test/support/sfinaes_away.h

15–28 ↗

(On Diff #383710)

Moved SFINAEs_away to deduction_guides_sfinae_checks.h.

I'd prefer to avoid duplication if possible. I had each test file have its own tests and definitions of everything in earlier states of this patch. It was a pain to modify, and I made some inevitable bugs forgetting to apply a change to all the relevant files.

[var-const]

libcxx/test/support/deduction_guides_sfinae_checks.h

23

(I mean SequenceContainerDeductionGuidesSfinaeAway and similar functions)

175

Note: alternatively, I could create a new struct for OutputIter, similar to the priority_queue test. Let me know if you'd prefer that.

[ldionne]

LGTM with the LIBCPP_STATIC_ASSERT simplification.

libcxx/test/std/containers/container.adaptors/priority.queue/priqueue.cons/deduct.pass.cpp

291

You can replace this by LIBCPP_STATIC_ASSERT and avoid the #ifdef dance.

libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/deduct.fail.cpp

9 ↗

(On Diff #383710)

Oh, then this is correct. It's a really unusual specification for this kind of failure though.

[var-const]

• use LIBCPP_STATIC_ASSERT;
• rebase on main.

[var-const]

Update the unique_ptr tests for the new wording in C++20.

[var-const]

libcxx/test/std/containers/container.adaptors/priority.queue/priqueue.cons/deduct.pass.cpp

291

Done, thanks!

libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/deduct.fail.cpp

9 ↗

(On Diff #383710)

I looked into this more closely, and there's actually been a change on this between C++17 and C++20.

In C++17, the requirement is:

If class template argument deduction would select the function template corresponding to this constructor, then the program is ill-formed.

However, [P1460](wg21.link/p1460) changed this in C++20 to:

Mandates: This constructor is not selected by class template argument deduction.

Now the words ill-formed are gone, and with the new wording, it seems like these constructors should just SFINAE away without causing a hard error. Moreover, this seems like a slight change in behavior. I don't see any discussion of this case in the paper, and I presume the new behavior is slightly more user-friendly.

It seems reasonable to me to only implement and test the new behavior, including in C++17 mode as well (FWIW, it was already implemented in a SFINAE-friendly way). Because of that, I replaced the previous deduct.fail.cpp file with a new deduct.pass.cpp test that uses SFINAEs_away. Let me know what you think!

[• Quuxplusone]

libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/deduct.fail.cpp

9 ↗

(On Diff #383710)

"Mandates" always means "static_assert, not SFINAE." When the standard means SFINAE, it uses "Constraints" instead. However, I think this is an editorial defect in p1460's changes: it replaced a soft "Remark" with a hard "Mandates." It should have said:

Remarks: This constructor is never selected by class template argument deduction.

or simply

unique_ptr(type_identity_t<pointer> p)

libstdc++ and MSVC both interpret the intent as "this constructor shouldn't contribute to CTAD," which matches what you settled on here, IIUC.
I'll email LWG suggesting a new issue to clarify this wording.

[• Quuxplusone]

libcxx/include/set

504

I vaguely recall hitting similar issues around CTAD in these containers, and suggesting that we firewall several (maybe all) of these member typedefs with __identity_t. But back then there was some reason we didn't do that. Probably just inertia, but I'm not sure. Looks like some discussion exists in D58587.

libcxx/include/vector

362

I still don't get this diff; but is it possible that it'll be a moot point after D112976?

libcxx/test/support/deduction_guides_sfinae_checks.h

24–33

Even after seeing @ldionne's comment, personally, I'd still write these tests without any additional headers. For a sequence container, we'd have this:

template<class... Args>
auto deque_has_no_ctad_from() -> decltype(std::deque(std::declval<Args>()...));
template<class... Args>
constexpr bool deque_has_no_ctad_from() { return true; }

int main(int, char**)
{
    // all the deduct.pass.cpp tests, and then these lines:

    using OutIt = std::insert_iterator<std::vector<int>>;
    struct NotAnAllocator {};

    LIBCPP_STATIC_ASSERT(deque_has_no_ctad_from<OutIt, OutIt>());
    LIBCPP_STATIC_ASSERT(deque_has_no_ctad_from<OutIt, OutIt, std::allocator<int>>());
    static_assert(deque_has_no_ctad_from<int*, int*, NotAnAllocator>());
}

And for an associative container like map we'd have this:

template<class... Args>
auto map_has_no_ctad_from() -> decltype(std::map(std::declval<Args>()...));
template<class... Args>
constexpr bool map_has_no_ctad_from() { return true; }

int main(int, char**)
{
    // all the deduct.pass.cpp tests, and then these lines:

    using VT = std::pair<const int, int>;
    using OutIt = std::insert_iterator<std::vector<int>>;
    struct NotAnAllocator {};

    static_assert(map_has_no_ctad_from<int, int>());
    static_assert(map_has_no_ctad_from<int, int, std::less<int>>());
    static_assert(map_has_no_ctad_from<int, int, std::allocator<VT>>());
    static_assert(map_has_no_ctad_from<int, int, std::less<int>, std::allocator<VT>>());
    LIBCPP_STATIC_ASSERT(map_has_no_ctad_from<OutIt, OutIt>());
    LIBCPP_STATIC_ASSERT(map_has_no_ctad_from<OutIt, OutIt, std::less<int>>());
    LIBCPP_STATIC_ASSERT(map_has_no_ctad_from<OutIt, OutIt, std::allocator<VT>>());
    LIBCPP_STATIC_ASSERT(map_has_no_ctad_from<OutIt, OutIt, std::less<int>, std::allocator<VT>>());
    static_assert(map_has_no_ctad_from<VT*, VT*, std::allocator<VT>, std::allocator<VT>>());
    static_assert(map_has_no_ctad_from<VT*, VT*, std::less<int>, NotAnAllocator>());
    LIBCPP_STATIC_ASSERT(map_has_no_ctad_from<std::initializer_list<VT>, std::allocator<VT>, std::allocator<VT>>);
    LIBCPP_STATIC_ASSERT(map_has_no_ctad_from<std::initializer_list<VT>, std::less<int>, NotAnAllocator>);
}

I just don't see the need for 300 lines of code off in test/support/ (plus another 100 lines in the priority_queue test) when we could have ~20 lines per container, right there in each container's test directory.

[var-const]

libcxx/include/vector

362

Without this change, the compiler errors out trying to instantiate allocator_traits with an incorrect allocator instead of silently SFINAE'ing away the deduction guide. However, like you said, it's a moot point after the other patch lands, so I don't think we need to spend time investigating this issue.

libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/deduct.fail.cpp

9 ↗

(On Diff #383710)

I'll email LWG suggesting a new issue to clarify this wording.

Thanks!

libcxx/test/support/deduction_guides_sfinae_checks.h

24–33

A better example would be the unordered containers which have 36 test cases per container. While we could reduce the line count by omitting comments, I find this state less readable and much harder to modify or to verify that every case is covered. While I was working on this patch, I had to change the tests multiple times, and I found comments to be very helpful when making changes. Moreover, duplicating each change at least 4 times is annoying and error-prone. Finally, if the tests were duplicated, the reader might have to manually compare different files to make sure they are exactly the same -- I have found several inconsistencies between similar duplicated tests while working on this patch. For these reasons, I'd prefer to keep the current state, even if it is more verbose.

I don't see the fact that the tests covering the same aspect of functionality are all in one place as a downside, necessarily. After all, most of these requirements are placed by the Standard on different classes of containers, not on individual containers.

What is the downside of adding a new header? I'm not sure why significant code duplication would be preferable, and my experience working on this patch suggests otherwise.

[var-const]

Rebase on main.

[• Quuxplusone]

libcxx/test/support/deduction_guides_sfinae_checks.h

24–33

What is the downside of adding a new header?

Just that it's always easier to understand code that's in one place, as opposed to having to skip back and forth between different files to get the full picture. Also for "attribution": when a test fails, it's nice to be able to point to the line that failed, which should be in the test that failed; having asserts in .h files included from multiple tests makes that just a bit harder. Also in case of later refactoring: suppose set and map have the same CTAD guides today, but then map gains one new guide tomorrow; with the "one line of code per test case" version, that's a one-line diff to add the new test case, but with the "everything calls into the same .h file" version, it might require arbitrarily invasive refactoring of the shared .h file. ("Copy-on-write," in other words.)
Basically, this is the software-engineering version of the "aliasing plus mutation" problem. Aliasing alone isn't a problem if everything is const; mutation alone isn't a problem if nothing is aliased; but combine aliasing with mutation and suddenly you have the potential for bugs and race conditions.
Which is not to say that plenty of programmers can't deal just fine with aliasing plus mutation. I mean, C++ does it. ;) So, having stated my view, I'll now let this thread be.

[var-const]

libcxx/test/support/deduction_guides_sfinae_checks.h

24–33

Thank you for the writeup! I still think that, given the amount of duplication, having common functions is the lesser evil in this case, but I understand your concerns much better now.

[var-const]

Rebase on main

[var-const]

Fix vector after merge.

libcxx/docs/Status/Cxx17.rst

 
 .. csv-table::
    :file: Cxx17Papers.csv
    :header-rows: 1
    :widths: auto
 
 .. note::
 
-   .. [#note-P0433] P0433: The only part not fully implemented is the requirement that certain deduction guides should not participate in overload resolution when given incorrect template arguments.
    .. [#note-P0607] P0607: The parts of P0607 that are not done are the ``<regex>`` bits.
 
 
 .. _issues-status-cxx17:
 
 Library Working Group Issues Status
 ====================================
 
 .. csv-table::
    :file: Cxx17Issues.csv
    :header-rows: 1
    :widths: auto

libcxx/docs/Status/Cxx17Papers.csv

 "`P0517R0 <https://wg21.link/P0517R0>`__","LWG","Make future_error Constructible","Issaquah","|Complete|","4.0"
 "`P0521R0 <https://wg21.link/P0521R0>`__","LWG","Proposed Resolution for CA 14 (shared_ptr use_count/unique)","Issaquah","|Nothing To Do|","n/a"
 "","","","","",""
 "`P0156R2 <https://wg21.link/P0156R2>`__","LWG","Variadic Lock guard(rev 5)","Kona","|Complete|","5.0"
 "`P0270R3 <https://wg21.link/P0270R3>`__","CWG","Removing C dependencies from signal handler wording","Kona","",""
 "`P0298R3 <https://wg21.link/P0298R3>`__","CWG","A byte type definition","Kona","|Complete|","5.0"
 "`P0317R1 <https://wg21.link/P0317R1>`__","LWG","Directory Entry Caching for Filesystem","Kona","|Complete|","7.0"
 "`P0430R2 <https://wg21.link/P0430R2>`__","LWG","File system library on non-POSIX-like operating systems","Kona","|Complete|","7.0"
-"`P0433R2 <https://wg21.link/P0433R2>`__","LWG","Toward a resolution of US7 and US14: Integrating template deduction for class templates into the standard library","Kona","|In Progress| [#note-P0433]_","7.0"
+"`P0433R2 <https://wg21.link/P0433R2>`__","LWG","Toward a resolution of US7 and US14: Integrating template deduction for class templates into the standard library","Kona","|Complete|","14.0"
 "`P0452R1 <https://wg21.link/P0452R1>`__","LWG","Unifying <numeric> Parallel Algorithms","Kona","",""
 "`P0467R2 <https://wg21.link/P0467R2>`__","LWG","Iterator Concerns for Parallel Algorithms","Kona","",""
 "`P0492R2 <https://wg21.link/P0492R2>`__","LWG","Proposed Resolution of C++17 National Body Comments for Filesystems","Kona","|Complete|","7.0"
 "`P0518R1 <https://wg21.link/P0518R1>`__","LWG","Allowing copies as arguments to function objects given to parallel algorithms in response to CH11","Kona","",""
 "`P0523R1 <https://wg21.link/P0523R1>`__","LWG","Wording for CH 10: Complexity of parallel algorithms","Kona","",""
 "`P0548R1 <https://wg21.link/P0548R1>`__","LWG","common_type and duration","Kona","|Complete|","5.0"
 "`P0558R1 <https://wg21.link/P0558R1>`__","LWG","Resolving atomic<T> named base class inconsistencies","Kona","|Complete|",""
 "`P0574R1 <https://wg21.link/P0574R1>`__","LWG","Algorithm Complexity Constraints and Parallel Overloads","Kona","",""
 "`P0599R1 <https://wg21.link/P0599R1>`__","LWG","noexcept for hash functions","Kona","|Complete|","5.0"
 "`P0604R0 <https://wg21.link/P0604R0>`__","LWG","Resolving GB 55, US 84, US 85, US 86","Kona","|Complete|",""
 "`P0607R0 <https://wg21.link/P0607R0>`__","LWG","Inline Variables for the Standard Library","Kona","|In Progress| [#note-P0607]_","6.0"
 "`P0618R0 <https://wg21.link/P0618R0>`__","LWG","Deprecating <codecvt>","Kona","",""
 "`P0623R0 <https://wg21.link/P0623R0>`__","LWG","Final C++17 Parallel Algorithms Fixes","Kona","",""
 "","","","","",""
 "`P0682R1 <https://wg21.link/P0682R1>`__","LWG","Repairing elementary string conversions","Toronto","",""
 "`P0739R0 <https://wg21.link/P0739R0>`__","LWG","Some improvements to class template argument deduction integration into the standard library","Toronto","|Complete|","5.0"

libcxx/include/__memory/allocator_traits.h

#endif
     template <class _Ap = _Alloc, class = void, class =
         __enable_if_t<!__has_select_on_container_copy_construction<const _Ap>::value> >
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     static allocator_type select_on_container_copy_construction(const allocator_type& __a) {
         return __a;
     }
 };
 
+// A version of `allocator_traits` for internal usage that SFINAEs away if the
+// given allocator doesn't have a nested `value_type`. This helps avoid hard
+// errors when forming implicit deduction guides for a container that has an
+// invalid Allocator type. See https://wg21.link/LWGXXXXX.
+// TODO(varconst): use the actual link once available.
+template <class _Alloc, class _ValueType = typename _Alloc::value_type>
+struct _LIBCPP_TEMPLATE_VIS __allocator_traits : allocator_traits<_Alloc> {};
+
 template <class _Traits, class _Tp>
 struct __rebind_alloc_helper {
 #ifndef _LIBCPP_CXX03_LANG
     using type _LIBCPP_NODEBUG = typename _Traits::template rebind_alloc<_Tp>;
 #else
     using type = typename _Traits::template rebind_alloc<_Tp>::other;
 #endif
 };

libcxx/include/deque

public:
     iterator erase(const_iterator f, const_iterator l);
     void swap(deque& c)
         noexcept(allocator_traits<allocator_type>::is_always_equal::value);  // C++17
     void clear() noexcept;
 };
 
 template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
    deque(InputIterator, InputIterator, Allocator = Allocator())
-   -> deque<typename iterator_traits<InputIterator>::value_type, Allocator>;
+   -> deque<typename iterator_traits<InputIterator>::value_type, Allocator>; // C++17
 
 template <class T, class Allocator>
     bool operator==(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
 template <class T, class Allocator>
     bool operator< (const deque<T,Allocator>& x, const deque<T,Allocator>& y);
 template <class T, class Allocator>
     bool operator!=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
 template <class T, class Allocator>
template <class T, class Allocator, class Predicate>
     erase_if(deque<T, Allocator>& c, Predicate pred);    // C++20
 
 }  // std
 
 */
 
 #include <__config>
 #include <__debug>
+#include <__iterator/iterator_traits.h>
 #include <__split_buffer>
 #include <__utility/forward.h>
 #include <algorithm>
 #include <compare>
 #include <initializer_list>
 #include <iterator>
 #include <limits>
 #include <stdexcept>
public:
     // types:
 
     typedef _Tp value_type;
     typedef _Allocator allocator_type;
 
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
-    typedef __deque_base<value_type, allocator_type> __base;
+    typedef __deque_base<value_type, allocator_type>                 __base;
 
-    typedef typename __base::__alloc_traits        __alloc_traits;
-    typedef typename __base::reference             reference;
-    typedef typename __base::const_reference       const_reference;
-    typedef typename __base::iterator              iterator;
-    typedef typename __base::const_iterator        const_iterator;
-    typedef typename __base::size_type             size_type;
-    typedef typename __base::difference_type       difference_type;
+    typedef typename __base::__alloc_traits                          __alloc_traits;
+    typedef typename __base::reference                               reference;
+    typedef typename __base::const_reference                         const_reference;
+    typedef typename __base::iterator                                iterator;
+    typedef typename __base::const_iterator                          const_iterator;
+    typedef typename __allocator_traits<allocator_type>::size_type   size_type;
+    typedef typename __base::difference_type                         difference_type;
 
-    typedef typename __base::pointer               pointer;
-    typedef typename __base::const_pointer         const_pointer;
-    typedef _VSTD::reverse_iterator<iterator>       reverse_iterator;
-    typedef _VSTD::reverse_iterator<const_iterator> const_reverse_iterator;
+    typedef typename __base::pointer                                 pointer;
+    typedef typename __base::const_pointer                           const_pointer;
+    typedef _VSTD::reverse_iterator<iterator>                        reverse_iterator;
+    typedef _VSTD::reverse_iterator<const_iterator>                  const_reverse_iterator;
 
     using typename __base::__deque_range;
     using typename __base::__deque_block_range;
     using typename __base::_ConstructTransaction;
 
     // construct/copy/destroy:
     _LIBCPP_INLINE_VISIBILITY
     deque()
private:
     void __move_assign(deque& __c, true_type)
         _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
     void __move_assign(deque& __c, false_type);
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Alloc = allocator<__iter_value_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value>
          >
 deque(_InputIterator, _InputIterator)
   -> deque<__iter_value_type<_InputIterator>, _Alloc>;
 
 template<class _InputIterator,
          class _Alloc,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value>
          >
 deque(_InputIterator, _InputIterator, _Alloc)
   -> deque<__iter_value_type<_InputIterator>, _Alloc>;
 #endif
 
-
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(size_type __n)
 {
     if (__n > 0)
         __append(__n);
 }
 
 #if _LIBCPP_STD_VER > 11

libcxx/include/forward_list

public:
 
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
     typedef value_type&                                                reference;
     typedef const value_type&                                          const_reference;
     typedef typename allocator_traits<allocator_type>::pointer         pointer;
     typedef typename allocator_traits<allocator_type>::const_pointer   const_pointer;
-    typedef typename allocator_traits<allocator_type>::size_type       size_type;
+    typedef typename __allocator_traits<allocator_type>::size_type     size_type;
     typedef typename allocator_traits<allocator_type>::difference_type difference_type;
 
     typedef typename base::iterator       iterator;
     typedef typename base::const_iterator const_iterator;
 #if _LIBCPP_STD_VER > 17
     typedef size_type                                __remove_return_type;
 #else
     typedef void                                     __remove_return_type;
template <class _Compare>
         __node_pointer
         __sort(__node_pointer __f, difference_type __sz, _Compare& __comp);
 };
 
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Alloc = allocator<__iter_value_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value>
          >
 forward_list(_InputIterator, _InputIterator)
   -> forward_list<__iter_value_type<_InputIterator>, _Alloc>;
 
 template<class _InputIterator,
          class _Alloc,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value>
          >
 forward_list(_InputIterator, _InputIterator, _Alloc)
   -> forward_list<__iter_value_type<_InputIterator>, _Alloc>;
 #endif
 
 template <class _Tp, class _Alloc>
 inline

libcxx/include/list

class _LIBCPP_TEMPLATE_VIS list
     typedef typename base::__node_allocator    __node_allocator;
     typedef typename base::__node_pointer      __node_pointer;
     typedef typename base::__node_alloc_traits __node_alloc_traits;
     typedef typename base::__node_base         __node_base;
     typedef typename base::__node_base_pointer __node_base_pointer;
     typedef typename base::__link_pointer __link_pointer;
 
 public:
-    typedef _Tp                                      value_type;
-    typedef _Alloc                                   allocator_type;
+    typedef _Tp                                                      value_type;
+    typedef _Alloc                                                   allocator_type;
     static_assert((is_same<value_type, typename allocator_type::value_type>::value),
                   "Invalid allocator::value_type");
-    typedef value_type&                              reference;
-    typedef const value_type&                        const_reference;
-    typedef typename base::pointer                   pointer;
-    typedef typename base::const_pointer             const_pointer;
-    typedef typename base::size_type                 size_type;
-    typedef typename base::difference_type           difference_type;
-    typedef typename base::iterator                  iterator;
-    typedef typename base::const_iterator            const_iterator;
-    typedef _VSTD::reverse_iterator<iterator>         reverse_iterator;
-    typedef _VSTD::reverse_iterator<const_iterator>   const_reverse_iterator;
+    typedef value_type&                                              reference;
+    typedef const value_type&                                        const_reference;
+    typedef typename base::pointer                                   pointer;
+    typedef typename base::const_pointer                             const_pointer;
+    typedef typename __allocator_traits<allocator_type>::size_type   size_type;
+    typedef typename base::difference_type                           difference_type;
+    typedef typename base::iterator                                  iterator;
+    typedef typename base::const_iterator                            const_iterator;
+    typedef _VSTD::reverse_iterator<iterator>                        reverse_iterator;
+    typedef _VSTD::reverse_iterator<const_iterator>                  const_reverse_iterator;
 #if _LIBCPP_STD_VER > 17
-    typedef size_type                                __remove_return_type;
+    typedef size_type                                                __remove_return_type;
 #else
-    typedef void                                     __remove_return_type;
+    typedef void                                                     __remove_return_type;
 #endif
 
     _LIBCPP_INLINE_VISIBILITY
     list()
         _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value)
     {
 #if _LIBCPP_DEBUG_LEVEL == 2
         __get_db()->__insert_c(this);
private:
     void __move_assign(list& __c, true_type)
         _NOEXCEPT_(is_nothrow_move_assignable<__node_allocator>::value);
     void __move_assign(list& __c, false_type);
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Alloc = allocator<__iter_value_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value>
          >
 list(_InputIterator, _InputIterator)
   -> list<__iter_value_type<_InputIterator>, _Alloc>;
 
 template<class _InputIterator,
          class _Alloc,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value>
          >
 list(_InputIterator, _InputIterator, _Alloc)
   -> list<__iter_value_type<_InputIterator>, _Alloc>;
 #endif
 
 // Link in nodes [__f, __l] just prior to __p
 template <class _Tp, class _Alloc>

libcxx/include/map

~map();
     pair<iterator,iterator>             equal_range(const key_type& k);
     pair<const_iterator,const_iterator> equal_range(const key_type& k) const;
     template<typename K>
         pair<iterator,iterator>             equal_range(const K& x);        // C++14
     template<typename K>
         pair<const_iterator,const_iterator> equal_range(const K& x) const;  // C++14
 };
 
+template <class InputIterator,
+      class Compare = less<iter_key_t<InputIterator>>,
+      class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
+map(InputIterator, InputIterator, Compare = Compare(), Allocator = Allocator())
+  -> map<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Compare, Allocator>; // C++17
+
+template<class Key, class T, class Compare = less<Key>,
+    class Allocator = allocator<pair<const Key, T>>>
+map(initializer_list<pair<const Key, T>>, Compare = Compare(), Allocator = Allocator())
+  -> map<Key, T, Compare, Allocator>; // C++17
+
+template <class InputIterator, class Allocator>
+map(InputIterator, InputIterator, Allocator)
+  -> map<iter_key_t<InputIterator>, iter_val_t<InputIterator>, less<iter_key_t<InputIterator>>,
+    Allocator>; // C++17
+
+template<class Key, class T, class Allocator>
+map(initializer_list<pair<const Key, T>>, Allocator) -> map<Key, T, less<Key>, Allocator>; // C++17
+
 template <class Key, class T, class Compare, class Allocator>
 bool
 operator==(const map<Key, T, Compare, Allocator>& x,
            const map<Key, T, Compare, Allocator>& y);
 
 template <class Key, class T, class Compare, class Allocator>
 bool
 operator< (const map<Key, T, Compare, Allocator>& x,
public:
     pair<iterator,iterator>             equal_range(const key_type& k);
     pair<const_iterator,const_iterator> equal_range(const key_type& k) const;
     template<typename K>
         pair<iterator,iterator>             equal_range(const K& x);        // C++14
     template<typename K>
         pair<const_iterator,const_iterator> equal_range(const K& x) const;  // C++14
 };
 
+template <class InputIterator,
+      class Compare = less<iter_key_t<InputIterator>>,
+      class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
+multimap(InputIterator, InputIterator, Compare = Compare(), Allocator = Allocator())
+  -> multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Compare, Allocator>; // C++17
+
+template<class Key, class T, class Compare = less<Key>,
+    class Allocator = allocator<pair<const Key, T>>>
+multimap(initializer_list<pair<const Key, T>>, Compare = Compare(), Allocator = Allocator())
+  -> multimap<Key, T, Compare, Allocator>; // C++17
+
+template <class InputIterator, class Allocator>
+multimap(InputIterator, InputIterator, Allocator)
+  -> multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
+    less<iter_key_t<InputIterator>>, Allocator>; // C++17
+
+template<class Key, class T, class Allocator>
+multimap(initializer_list<pair<const Key, T>>, Allocator)
+  -> multimap<Key, T, less<Key>, Allocator>; // C++17
+
 template <class Key, class T, class Compare, class Allocator>
 bool
 operator==(const multimap<Key, T, Compare, Allocator>& x,
            const multimap<Key, T, Compare, Allocator>& y);
 
 template <class Key, class T, class Compare, class Allocator>
 bool
 operator< (const multimap<Key, T, Compare, Allocator>& x,

 
 }  // std
 
 */
 
 #include <__config>
 #include <__debug>
 #include <__functional/is_transparent.h>
+#include <__iterator/iterator_traits.h>
 #include <__node_handle>
 #include <__tree>
 #include <__utility/forward.h>
 #include <compare>
 #include <functional>
 #include <initializer_list>
 #include <iterator> // __libcpp_erase_if_container
 #include <memory>

 #ifdef _LIBCPP_CXX03_LANG
     __node_holder __construct_node_with_key(const key_type& __k);
 #endif
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator, class _Compare = less<__iter_key_type<_InputIterator>>,
          class _Allocator = allocator<__iter_to_alloc_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>,
          class = enable_if_t<!__is_allocator<_Compare>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 map(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
   -> map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Compare, _Allocator>;
 
 template<class _Key, class _Tp, class _Compare = less<remove_const_t<_Key>>,
          class _Allocator = allocator<pair<const _Key, _Tp>>,
          class = enable_if_t<!__is_allocator<_Compare>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 map(initializer_list<pair<_Key, _Tp>>, _Compare = _Compare(), _Allocator = _Allocator())
   -> map<remove_const_t<_Key>, _Tp, _Compare, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 map(_InputIterator, _InputIterator, _Allocator)
   -> map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
          less<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _Key, class _Tp, class _Allocator,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 map(initializer_list<pair<_Key, _Tp>>, _Allocator)
private:
 
     typedef __map_node_destructor<__node_allocator> _Dp;
     typedef unique_ptr<__node, _Dp> __node_holder;
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator, class _Compare = less<__iter_key_type<_InputIterator>>,
          class _Allocator = allocator<__iter_to_alloc_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>,
          class = enable_if_t<!__is_allocator<_Compare>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 multimap(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
   -> multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Compare, _Allocator>;
 
 template<class _Key, class _Tp, class _Compare = less<remove_const_t<_Key>>,
          class _Allocator = allocator<pair<const _Key, _Tp>>,
          class = enable_if_t<!__is_allocator<_Compare>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 multimap(initializer_list<pair<_Key, _Tp>>, _Compare = _Compare(), _Allocator = _Allocator())
   -> multimap<remove_const_t<_Key>, _Tp, _Compare, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 multimap(_InputIterator, _InputIterator, _Allocator)
   -> multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
          less<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _Key, class _Tp, class _Allocator,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 multimap(initializer_list<pair<_Key, _Tp>>, _Allocator)

libcxx/include/queue

 template<class Compare, class Container, class Allocator>
 priority_queue(Compare, Container, Allocator)
     -> priority_queue<typename Container::value_type, Container, Compare>; // C++17
 
 template<class InputIterator, class Allocator>
 priority_queue(InputIterator, InputIterator, Allocator)
     -> priority_queue<iter-value-type<InputIterator>,
                       vector<iter-value-type<InputIterator>, Allocator>,
-                      less<iter-value-type<InputIterator>>>;
+                      less<iter-value-type<InputIterator>>>; // C++17
 
 template<class InputIterator, class Compare, class Allocator>
 priority_queue(InputIterator, InputIterator, Compare, Allocator)
     -> priority_queue<iter-value-type<InputIterator>,
-                      vector<iter-value-type<InputIterator>, Allocator>, Compare>;
+                      vector<iter-value-type<InputIterator>, Allocator>, Compare>; // C++17
 
 template<class InputIterator, class Compare, class Container, class Allocator>
 priority_queue(InputIterator, InputIterator, Compare, Container, Allocator)
-    -> priority_queue<typename Container::value_type, Container, Compare>;
+    -> priority_queue<typename Container::value_type, Container, Compare>; // C++17
 
 template <class T, class Container, class Compare>
   void swap(priority_queue<T, Container, Compare>& x,
             priority_queue<T, Container, Compare>& y)
             noexcept(noexcept(x.swap(y)));
 
 }  // std
 

libcxx/include/set

public:
     pair<iterator,iterator>             equal_range(const key_type& k);
     pair<const_iterator,const_iterator> equal_range(const key_type& k) const;
     template<typename K>
         pair<iterator,iterator>             equal_range(const K& x);        // C++14
     template<typename K>
         pair<const_iterator,const_iterator> equal_range(const K& x) const;  // C++14
 };
 
+template <class InputIterator,
+      class Compare = less<typename iterator_traits<InputIterator>::value_type>,
+      class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
+set(InputIterator, InputIterator,
+    Compare = Compare(), Allocator = Allocator())
+  -> set<typename iterator_traits<InputIterator>::value_type, Compare, Allocator>; // C++17
+
+template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
+set(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
+  -> set<Key, Compare, Allocator>; // C++17
+
+template<class InputIterator, class Allocator>
+set(InputIterator, InputIterator, Allocator)
+  -> set<typename iterator_traits<InputIterator>::value_type,
+          less<typename iterator_traits<InputIterator>::value_type>, Allocator>; // C++17
+
+template<class Key, class Allocator>
+set(initializer_list<Key>, Allocator) -> set<Key, less<Key>, Allocator>; // C++17
+
 template <class Key, class Compare, class Allocator>
 bool
 operator==(const set<Key, Compare, Allocator>& x,
            const set<Key, Compare, Allocator>& y);
 
 template <class Key, class Compare, class Allocator>
 bool
 operator< (const set<Key, Compare, Allocator>& x,
public:
     pair<iterator,iterator>             equal_range(const key_type& k);
     pair<const_iterator,const_iterator> equal_range(const key_type& k) const;
     template<typename K>
         pair<iterator,iterator>             equal_range(const K& x);        // C++14
     template<typename K>
         pair<const_iterator,const_iterator> equal_range(const K& x) const;  // C++14
 };
 
+template <class InputIterator,
+      class Compare = less<typename iterator_traits<InputIterator>::value_type>,
+      class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
+multiset(InputIterator, InputIterator,
+    Compare = Compare(), Allocator = Allocator())
+  -> multiset<typename iterator_traits<InputIterator>::value_type, Compare, Allocator>; // C++17
+
+template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
+multiset(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
+  -> multiset<Key, Compare, Allocator>; // C++17
+
+template<class InputIterator, class Allocator>
+multiset(InputIterator, InputIterator, Allocator)
+  -> multiset<typename iterator_traits<InputIterator>::value_type,
+          less<typename iterator_traits<InputIterator>::value_type>, Allocator>; // C++17
+
+template<class Key, class Allocator>
+multiset(initializer_list<Key>, Allocator) -> multiset<Key, less<Key>, Allocator>; // C++17
+
 template <class Key, class Compare, class Allocator>
 bool
 operator==(const multiset<Key, Compare, Allocator>& x,
            const multiset<Key, Compare, Allocator>& y);
 
 template <class Key, class Compare, class Allocator>
 bool
 operator< (const multiset<Key, Compare, Allocator>& x,

 
 }  // std
 
 */
 
 #include <__config>
 #include <__debug>
 #include <__functional/is_transparent.h>
+#include <__iterator/iterator_traits.h>
 #include <__node_handle>
 #include <__tree>
 #include <__utility/forward.h>
 #include <compare>
 #include <functional>
 #include <initializer_list>
 #include <iterator> // __libcpp_erase_if_container
 #include <version>

 template <class _Key, class _Compare = less<_Key>,
           class _Allocator = allocator<_Key> >
 class _LIBCPP_TEMPLATE_VIS set
 {
 public:
     // types:
     typedef _Key                                     key_type;
     typedef key_type                                 value_type;
-    typedef _Compare                                 key_compare;
+    typedef __identity_t<_Compare>                   key_compare;
     typedef key_compare                              value_compare;
     typedef __identity_t<_Allocator>                 allocator_type;
     typedef value_type&                              reference;
     typedef const value_type&                        const_reference;
 
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
 private:
     typedef __tree<value_type, value_compare, allocator_type> __base;
     typedef allocator_traits<allocator_type>                  __alloc_traits;
-    typedef typename __base::__node_holder                    __node_holder;
 
     __base __tree_;
 
 public:
     typedef typename __base::pointer               pointer;
     typedef typename __base::const_pointer         const_pointer;
     typedef typename __base::size_type             size_type;
     typedef typename __base::difference_type       difference_type;
#if _LIBCPP_STD_VER > 11
     equal_range(const _K2& __k) const {return __tree_.__equal_range_multi(__k);}
 #endif
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Compare = less<__iter_value_type<_InputIterator>>,
          class _Allocator = allocator<__iter_value_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>,
          class = enable_if_t<!__is_allocator<_Compare>::value, void>>
 set(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
   -> set<__iter_value_type<_InputIterator>, _Compare, _Allocator>;
 
 template<class _Key, class _Compare = less<_Key>,
          class _Allocator = allocator<_Key>,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>,
-         class = enable_if_t<!__is_allocator<_Compare>::value, void>>
+         class = enable_if_t<!__is_allocator<_Compare>::value, void>,
+         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 set(initializer_list<_Key>, _Compare = _Compare(), _Allocator = _Allocator())
   -> set<_Key, _Compare, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 set(_InputIterator, _InputIterator, _Allocator)
   -> set<__iter_value_type<_InputIterator>,
          less<__iter_value_type<_InputIterator>>, _Allocator>;
 
 template<class _Key, class _Allocator,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 set(initializer_list<_Key>, _Allocator)

 template <class _Key, class _Compare = less<_Key>,
           class _Allocator = allocator<_Key> >
 class _LIBCPP_TEMPLATE_VIS multiset
 {
 public:
     // types:
     typedef _Key                                     key_type;
     typedef key_type                                 value_type;
-    typedef _Compare                                 key_compare;
+    typedef __identity_t<_Compare>                   key_compare;
     typedef key_compare                              value_compare;
     typedef __identity_t<_Allocator>                 allocator_type;
     typedef value_type&                              reference;
     typedef const value_type&                        const_reference;
 
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
 private:
     typedef __tree<value_type, value_compare, allocator_type> __base;
     typedef allocator_traits<allocator_type>                  __alloc_traits;
-    typedef typename __base::__node_holder                    __node_holder;
 
     __base __tree_;
 
 public:
     typedef typename __base::pointer               pointer;
     typedef typename __base::const_pointer         const_pointer;
     typedef typename __base::size_type             size_type;
     typedef typename __base::difference_type       difference_type;
#if _LIBCPP_STD_VER > 11
     equal_range(const _K2& __k) const {return __tree_.__equal_range_multi(__k);}
 #endif
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Compare = less<__iter_value_type<_InputIterator>>,
          class _Allocator = allocator<__iter_value_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>,
          class = enable_if_t<!__is_allocator<_Compare>::value, void>>
 multiset(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
   -> multiset<__iter_value_type<_InputIterator>, _Compare, _Allocator>;
 
 template<class _Key, class _Compare = less<_Key>,
          class _Allocator = allocator<_Key>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>,
          class = enable_if_t<!__is_allocator<_Compare>::value, void>>
 multiset(initializer_list<_Key>, _Compare = _Compare(), _Allocator = _Allocator())
   -> multiset<_Key, _Compare, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 multiset(_InputIterator, _InputIterator, _Allocator)
   -> multiset<__iter_value_type<_InputIterator>,
          less<__iter_value_type<_InputIterator>>, _Allocator>;
 
 template<class _Key, class _Allocator,
          class = enable_if_t<__is_allocator<_Allocator>::value, void>>
 multiset(initializer_list<_Key>, _Allocator)

libcxx/include/unordered_map

public:
 
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
 };
 
+template<class InputIterator,
+    class Hash = hash<iter_key_t<InputIterator>>, class Pred = equal_to<iter_key_t<InputIterator>>,
+    class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
+unordered_map(InputIterator, InputIterator, typename see below::size_type = see below,
+    Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+  -> unordered_map<iter_key_t<InputIterator>, iter_value_t<InputIterator>, Hash, Pred,
+    Allocator>; // C++17
+
+template<class Key, class T, class Hash = hash<Key>,
+    class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
+unordered_map(initializer_list<pair<const Key, T>>, typename see below::size_type = see below,
+    Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+  -> unordered_map<Key, T, Hash, Pred, Allocator>; // C++17
+
+template<class InputIterator, class Allocator>
+unordered_map(InputIterator, InputIterator, typename see below::size_type, Allocator)
+  -> unordered_map<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
+        hash<iter_key_t<InputIterator>>, equal_to<iter_key_t<InputIterator>>, Allocator>; // C++17
+
+template<class InputIterator, class Allocator>
+unordered_map(InputIterator, InputIterator, Allocator)
+  -> unordered_map<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
+        hash<iter_key_t<InputIterator>>, equal_to<iter_key_t<InputIterator>>, Allocator>; // C++17
+
+template<class InputIterator, class Hash, class Allocator>
+unordered_map(InputIterator, InputIterator, typename see below::size_type, Hash, Allocator)
+  -> unordered_map<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Hash,
+          equal_to<iter_key_t<InputIterator>>, Allocator>; // C++17
+
+template<class Key, class T, typename Allocator>
+unordered_map(initializer_list<pair<const Key, T>>, typename see below::size_type, Allocator)
+  -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>; // C++17
+
+template<class Key, class T, typename Allocator>
+unordered_map(initializer_list<pair<const Key, T>>, Allocator)
+  -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>; // C++17
+
+template<class Key, class T, class Hash, class Allocator>
+unordered_map(initializer_list<pair<const Key, T>>, typename see below::size_type, Hash, Allocator)
+  -> unordered_map<Key, T, Hash, equal_to<Key>, Allocator>; // C++17
+
 template <class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x,
               unordered_map<Key, T, Hash, Pred, Alloc>& y)
               noexcept(noexcept(x.swap(y)));
 
 template <class Key, class T, class Hash, class Pred, class Alloc>
     bool
     operator==(const unordered_map<Key, T, Hash, Pred, Alloc>& x,
public:
 
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
 };
 
+template<class InputIterator,
+    class Hash = hash<iter_key_t<InputIterator>>, class Pred = equal_to<iter_key_t<InputIterator>>,
+    class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
+unordered_multimap(InputIterator, InputIterator, typename see below::size_type = see below,
+    Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+  -> unordered_multimap<iter_key_t<InputIterator>, iter_value_t<InputIterator>, Hash, Pred,
+    Allocator>; // C++17
+
+template<class Key, class T, class Hash = hash<Key>,
+    class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
+unordered_multimap(initializer_list<pair<const Key, T>>, typename see below::size_type = see below,
+    Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+  -> unordered_multimap<Key, T, Hash, Pred, Allocator>; // C++17
+
+template<class InputIterator, class Allocator>
+unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Allocator)
+  -> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
+        hash<iter_key_t<InputIterator>>, equal_to<iter_key_t<InputIterator>>, Allocator>; // C++17
+
+template<class InputIterator, class Allocator>
+unordered_multimap(InputIterator, InputIterator, Allocator)
+  -> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
+        hash<iter_key_t<InputIterator>>, equal_to<iter_key_t<InputIterator>>, Allocator>; // C++17
+
+template<class InputIterator, class Hash, class Allocator>
+unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Hash, Allocator)
+  -> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Hash,
+          equal_to<iter_key_t<InputIterator>>, Allocator>; // C++17
+
+template<class Key, class T, typename Allocator>
+unordered_multimap(initializer_list<pair<const Key, T>>, typename see below::size_type, Allocator)
+  -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>; // C++17
+
+template<class Key, class T, typename Allocator>
+unordered_multimap(initializer_list<pair<const Key, T>>, Allocator)
+  -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>; // C++17
+
+template<class Key, class T, class Hash, class Allocator>
+unordered_multimap(initializer_list<pair<const Key, T>>, typename see below::size_type, Hash,
+    Allocator)
+  -> unordered_multimap<Key, T, Hash, equal_to<Key>, Allocator>; // C++17
+
 template <class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
               unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
               noexcept(noexcept(x.swap(y)));
 
 template <class K, class T, class H, class P, class A, class Predicate>
     typename unordered_map<K, T, H, P, A>::size_type
     erase_if(unordered_map<K, T, H, P, A>& c, Predicate pred);       // C++20

 
 }  // std
 
 */
 
 #include <__config>
 #include <__debug>
 #include <__functional/is_transparent.h>
+#include <__iterator/iterator_traits.h>
 #include <__hash_table>
 #include <__node_handle>
 #include <__utility/forward.h>
 #include <compare>
 #include <functional>
 #include <iterator> // __libcpp_erase_if_container
 #include <stdexcept>
 #include <tuple>

 #endif
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Hash = hash<__iter_key_type<_InputIterator>>,
          class _Pred = equal_to<__iter_key_type<_InputIterator>>,
          class _Allocator = allocator<__iter_to_alloc_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<!__is_allocator<_Pred>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_map(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type = 0,
               _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
   -> unordered_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Hash, _Pred, _Allocator>;
 
 template<class _Key, class _Tp, class _Hash = hash<remove_const_t<_Key>>,
          class _Pred = equal_to<remove_const_t<_Key>>,
          class _Allocator = allocator<pair<const _Key, _Tp>>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<!__is_allocator<_Pred>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_map(initializer_list<pair<_Key, _Tp>>, typename allocator_traits<_Allocator>::size_type = 0,
               _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
   -> unordered_map<remove_const_t<_Key>, _Tp, _Hash, _Pred, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_map(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Allocator)
   -> unordered_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
                    hash<__iter_key_type<_InputIterator>>, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_map(_InputIterator, _InputIterator, _Allocator)
   -> unordered_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
                    hash<__iter_key_type<_InputIterator>>, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _InputIterator, class _Hash, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_map(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
   -> unordered_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
                    _Hash, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _Key, class _Tp, class _Allocator,

 
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Hash = hash<__iter_key_type<_InputIterator>>,
          class _Pred = equal_to<__iter_key_type<_InputIterator>>,
          class _Allocator = allocator<__iter_to_alloc_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<!__is_allocator<_Pred>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multimap(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type = 0,
                    _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
   -> unordered_multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Hash, _Pred, _Allocator>;
 
 template<class _Key, class _Tp, class _Hash = hash<remove_const_t<_Key>>,
          class _Pred = equal_to<remove_const_t<_Key>>,
          class _Allocator = allocator<pair<const _Key, _Tp>>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<!__is_allocator<_Pred>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multimap(initializer_list<pair<_Key, _Tp>>, typename allocator_traits<_Allocator>::size_type = 0,
                    _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
   -> unordered_multimap<remove_const_t<_Key>, _Tp, _Hash, _Pred, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multimap(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Allocator)
   -> unordered_multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
                         hash<__iter_key_type<_InputIterator>>, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multimap(_InputIterator, _InputIterator, _Allocator)
   -> unordered_multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
                         hash<__iter_key_type<_InputIterator>>, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _InputIterator, class _Hash, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multimap(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
   -> unordered_multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
                         _Hash, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _Key, class _Tp, class _Allocator,

libcxx/include/unordered_set

public:
 
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
 };
 
+template<class InputIterator,
+    class Hash = hash<typename iterator_traits<InputIterator>::value_type>,
+    class Pred = equal_to<typename iterator_traits<InputIterator>::value_type>,
+    class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
+unordered_set(InputIterator, InputIterator, typename see below::size_type = see below,
+    Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+  -> unordered_set<typename iterator_traits<InputIterator>::value_type,
+        Hash, Pred, Allocator>; // C++17
+
+template<class T, class Hash = hash<T>,
+          class Pred = equal_to<T>, class Allocator = allocator<T>>
+unordered_set(initializer_list<T>, typename see below::size_type = see below,
+    Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+  -> unordered_set<T, Hash, Pred, Allocator>; // C++17
+
+template<class InputIterator,  class Allocator>
+unordered_set(InputIterator, InputIterator, typename see below::size_type, Allocator)
+  -> unordered_set<typename iterator_traits<InputIterator>::value_type,
+        hash<typename iterator_traits<InputIterator>::value_type>,
+        equal_to<typename iterator_traits<InputIterator>::value_type>,
+        Allocator>; // C++17
+
+template<class InputIterator, class Hash, class Allocator>
+unordered_set(InputIterator, InputIterator, typename see below::size_type,
+    Hash, Allocator)
+  -> unordered_set<typename iterator_traits<InputIterator>::value_type, Hash,
+        equal_to<typename iterator_traits<InputIterator>::value_type>,
+        Allocator>; // C++17
+
+template<class T, class Allocator>
+unordered_set(initializer_list<T>, typename see below::size_type, Allocator)
+  -> unordered_set<T, hash<T>, equal_to<T>, Allocator>; // C++17
+
+template<class T, class Hash, class Allocator>
+unordered_set(initializer_list<T>, typename see below::size_type, Hash, Allocator)
+  -> unordered_set<T, Hash, equal_to<T>, Allocator>; // C++17
+
 template <class Value, class Hash, class Pred, class Alloc>
     void swap(unordered_set<Value, Hash, Pred, Alloc>& x,
               unordered_set<Value, Hash, Pred, Alloc>& y)
               noexcept(noexcept(x.swap(y)));
 
 template <class Value, class Hash, class Pred, class Alloc>
     bool
     operator==(const unordered_set<Value, Hash, Pred, Alloc>& x,
public:
 
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
 };
 
+template<class InputIterator,
+    class Hash = hash<typename iterator_traits<InputIterator>::value_type>,
+    class Pred = equal_to<typename iterator_traits<InputIterator>::value_type>,
+    class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
+unordered_multiset(InputIterator, InputIterator, see below::size_type = see below,
+    Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+  -> unordered_multiset<typename iterator_traits<InputIterator>::value_type,
+        Hash, Pred, Allocator>; // C++17
+
+template<class T, class Hash = hash<T>,
+          class Pred = equal_to<T>, class Allocator = allocator<T>>
+unordered_multiset(initializer_list<T>, typename see below::size_type = see below,
+    Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+  -> unordered_multiset<T, Hash, Pred, Allocator>; // C++17
+
+template<class InputIterator,  class Allocator>
+unordered_multiset(InputIterator, InputIterator, typename see below::size_type, Allocator)
+  -> unordered_multiset<typename iterator_traits<InputIterator>::value_type,
+        hash<typename iterator_traits<InputIterator>::value_type>,
+        equal_to<typename iterator_traits<InputIterator>::value_type>,
+        Allocator>; // C++17
+
+template<class InputIterator,  class Hash, class Allocator>
+unordered_multiset(InputIterator, InputIterator, typename see below::size_type,
+    Hash, Allocator)
+  -> unordered_multiset<typename iterator_traits<InputIterator>::value_type, Hash,
+        equal_to<typename iterator_traits<InputIterator>::value_type>, Allocator>; // C++17
+
+template<class T, class Allocator>
+unordered_multiset(initializer_list<T>, typename see below::size_type, Allocator)
+  -> unordered_multiset<T, hash<T>, equal_to<T>, Allocator>; // C++17
+
+template<class T, class Hash, class Allocator>
+unordered_multiset(initializer_list<T>, typename see below::size_type, Hash, Allocator)
+  -> unordered_multiset<T, Hash, equal_to<T>, Allocator>; // C++17
+
 template <class Value, class Hash, class Pred, class Alloc>
     void swap(unordered_multiset<Value, Hash, Pred, Alloc>& x,
               unordered_multiset<Value, Hash, Pred, Alloc>& y)
               noexcept(noexcept(x.swap(y)));
 
 template <class K, class T, class H, class P, class A, class Predicate>
     typename unordered_set<K, T, H, P, A>::size_type
     erase_if(unordered_set<K, T, H, P, A>& c, Predicate pred);       // C++20

 
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Hash = hash<__iter_value_type<_InputIterator>>,
          class _Pred = equal_to<__iter_value_type<_InputIterator>>,
          class _Allocator = allocator<__iter_value_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<!__is_allocator<_Pred>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_set(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type = 0,
               _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
   -> unordered_set<__iter_value_type<_InputIterator>, _Hash, _Pred, _Allocator>;
 
 template<class _Tp, class _Hash = hash<_Tp>,
          class _Pred = equal_to<_Tp>,
          class _Allocator = allocator<_Tp>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<!__is_allocator<_Pred>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_set(initializer_list<_Tp>, typename allocator_traits<_Allocator>::size_type = 0,
               _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
   -> unordered_set<_Tp, _Hash, _Pred, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_set(_InputIterator, _InputIterator,
               typename allocator_traits<_Allocator>::size_type, _Allocator)
   -> unordered_set<__iter_value_type<_InputIterator>,
                    hash<__iter_value_type<_InputIterator>>,
                    equal_to<__iter_value_type<_InputIterator>>,
                    _Allocator>;
 
 template<class _InputIterator, class _Hash, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_set(_InputIterator, _InputIterator,
               typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
   -> unordered_set<__iter_value_type<_InputIterator>, _Hash,
                    equal_to<__iter_value_type<_InputIterator>>,
                    _Allocator>;

 
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Hash = hash<__iter_value_type<_InputIterator>>,
          class _Pred = equal_to<__iter_value_type<_InputIterator>>,
          class _Allocator = allocator<__iter_value_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<!__is_allocator<_Pred>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multiset(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type = 0,
               _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
   -> unordered_multiset<__iter_value_type<_InputIterator>, _Hash, _Pred, _Allocator>;
 
 template<class _Tp, class _Hash = hash<_Tp>,
          class _Pred = equal_to<_Tp>, class _Allocator = allocator<_Tp>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<!__is_allocator<_Pred>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multiset(initializer_list<_Tp>, typename allocator_traits<_Allocator>::size_type = 0,
               _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
   -> unordered_multiset<_Tp, _Hash, _Pred, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multiset(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Allocator)
   -> unordered_multiset<__iter_value_type<_InputIterator>,
                    hash<__iter_value_type<_InputIterator>>,
                    equal_to<__iter_value_type<_InputIterator>>,
                    _Allocator>;
 
 template<class _InputIterator, class _Hash, class _Allocator,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<!__is_allocator<_Hash>::value>,
          class = enable_if_t<!is_integral<_Hash>::value>,
          class = enable_if_t<__is_allocator<_Allocator>::value>>
 unordered_multiset(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type,
               _Hash, _Allocator)
   -> unordered_multiset<__iter_value_type<_InputIterator>, _Hash,
                    equal_to<__iter_value_type<_InputIterator>>,
                    _Allocator>;

libcxx/include/vector

void swap(vector&)
                  allocator_traits<allocator_type>::is_always_equal::value);  // C++17
     void flip() noexcept;
 
     bool __invariants() const;
 };
 
 template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
    vector(InputIterator, InputIterator, Allocator = Allocator())
-   -> vector<typename iterator_traits<InputIterator>::value_type, Allocator>;
+   -> vector<typename iterator_traits<InputIterator>::value_type, Allocator>; // C++17
 
 template <class Allocator> struct hash<std::vector<bool, Allocator>>;
 
 template <class T, class Allocator> bool operator==(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
 template <class T, class Allocator> bool operator< (const vector<T,Allocator>& x, const vector<T,Allocator>& y);
 template <class T, class Allocator> bool operator!=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
 template <class T, class Allocator> bool operator> (const vector<T,Allocator>& x, const vector<T,Allocator>& y);
 template <class T, class Allocator> bool operator>=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);

 }  // std
 
 */
 
 #include <__config>
 #include <__bit_reference>
 #include <__debug>
 #include <__functional_base>
+#include <__iterator/iterator_traits.h>
 #include <__iterator/wrap_iter.h>
 #include <__split_buffer>
 #include <__utility/forward.h>
 #include <algorithm>
 #include <climits>
 #include <compare>
 #include <cstdlib>
 #include <cstring>

 };
 
 template <class _Tp, class _Allocator /* = allocator<_Tp> */>
 class _LIBCPP_TEMPLATE_VIS vector
     // This base class is historical, but it needs to remain for ABI compatibility.
     : private __vector_base<_Tp, _Allocator>
 {
 private:
-    typedef __vector_base<_Tp, _Allocator>           __base;
-    typedef allocator<_Tp>                           __default_allocator_type;
+    typedef __vector_base<_Tp, _Allocator>                           __base;
+    typedef allocator<_Tp>                                           __default_allocator_type;
 public:
-    typedef vector                                   __self;
-    typedef _Tp                                      value_type;
-    typedef _Allocator                               allocator_type;
-    typedef allocator_traits<allocator_type>         __alloc_traits;
-    typedef value_type&                              reference;
-    typedef const value_type&                        const_reference;
-    typedef typename __alloc_traits::size_type       size_type;
-    typedef typename __alloc_traits::difference_type difference_type;
-    typedef typename __alloc_traits::pointer         pointer;
-    typedef typename __alloc_traits::const_pointer   const_pointer;
-    typedef __wrap_iter<pointer>                     iterator;
-    typedef __wrap_iter<const_pointer>               const_iterator;
-    typedef _VSTD::reverse_iterator<iterator>        reverse_iterator;
+    typedef vector                                                   __self;
+    typedef _Tp                                                      value_type;
+    typedef _Allocator                                               allocator_type;
+    typedef allocator_traits<allocator_type>                         __alloc_traits;
+    typedef value_type&                                              reference;
+    typedef const value_type&                                        const_reference;
+    typedef typename __allocator_traits<allocator_type>::size_type   size_type;
+    typedef typename __alloc_traits::difference_type                 difference_type;
+    typedef typename __alloc_traits::pointer                         pointer;
+    typedef typename __alloc_traits::const_pointer                   const_pointer;
+    typedef __wrap_iter<pointer>                                     iterator;
+    typedef __wrap_iter<const_pointer>                               const_iterator;
+    typedef _VSTD::reverse_iterator<iterator>                        reverse_iterator;
     typedef _VSTD::reverse_iterator<const_iterator>  const_reverse_iterator;
 
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
     _LIBCPP_INLINE_VISIBILITY
     vector() _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
         {
#endif
   void __move_assign_alloc(vector&, false_type)
       _NOEXCEPT
   {}
 };
 
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Alloc = allocator<__iter_value_type<_InputIterator>>,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value>
          >
 vector(_InputIterator, _InputIterator)
   -> vector<__iter_value_type<_InputIterator>, _Alloc>;
 
 template<class _InputIterator,
          class _Alloc,
+         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value>
          >
 vector(_InputIterator, _InputIterator, _Alloc)
   -> vector<__iter_value_type<_InputIterator>, _Alloc>;
 #endif
 
 template <class _Tp, class _Allocator>
 void

libcxx/test/std/containers/associative/map/map.cons/deduct.pass.cpp

 
 #include <algorithm> // std::equal
 #include <cassert>
 #include <climits> // INT_MAX
 #include <functional>
 #include <map>
 #include <type_traits>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_allocator.h"
 
 using P = std::pair<int, long>;
 using PC = std::pair<const int, long>;
 
 int main(int, char**)
 {
     {
int main(int, char**)
     std::map m1{{std::pair{1, 2}, {3, 4}}, std::less<int>()};
     ASSERT_SAME_TYPE(decltype(m1), std::map<int, int>);
 
     using value_type = std::pair<const int, int>;
     std::map m2{{value_type{1, 2}, {3, 4}}, std::less<int>()};
     ASSERT_SAME_TYPE(decltype(m2), std::map<int, int>);
     }
 
+    AssociativeContainerDeductionGuidesSfinaeAway<std::map, std::map<int, long>>();
+
     return 0;
 }

libcxx/test/std/containers/associative/multimap/multimap.cons/deduct.pass.cpp

 
 #include <algorithm> // std::equal
 #include <cassert>
 #include <climits> // INT_MAX
 #include <functional>
 #include <map>
 #include <type_traits>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_allocator.h"
 
 using P = std::pair<int, long>;
 using PC = std::pair<const int, long>;
 
 int main(int, char**)
 {
     {
int main(int, char**)
     std::multimap m1{{std::pair{1, 2}, {3, 4}}, std::less<int>()};
     ASSERT_SAME_TYPE(decltype(m1), std::multimap<int, int>);
 
     using value_type = std::pair<const int, int>;
     std::multimap m2{{value_type{1, 2}, {3, 4}}, std::less<int>()};
     ASSERT_SAME_TYPE(decltype(m2), std::multimap<int, int>);
     }
 
+    AssociativeContainerDeductionGuidesSfinaeAway<std::multimap, std::multimap<int, long>>();
+
     return 0;
 }

libcxx/test/std/containers/associative/multiset/multiset.cons/deduct.pass.cpp

 
 #include <algorithm> // std::equal
 #include <cassert>
 #include <climits> // INT_MAX
 #include <functional>
 #include <set>
 #include <type_traits>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_allocator.h"
 
 struct NotAnAllocator {
   friend bool operator<(NotAnAllocator, NotAnAllocator) { return false; }
 };
 
 int main(int, char **) {
   {
int main(int, char **) {
 
   {
     int source[3] = { 3, 4, 5 };
     std::multiset s{ source, source + 3 }; // multiset(initializer_list<int*>)
     ASSERT_SAME_TYPE(decltype(s), std::multiset<int *>);
     assert(s.size() == 2);
   }
 
+  AssociativeContainerDeductionGuidesSfinaeAway<std::multiset, std::multiset<int>>();
+
   return 0;
 }

libcxx/test/std/containers/associative/set/set.cons/deduct.pass.cpp

 
 #include <algorithm> // std::equal
 #include <cassert>
 #include <climits> // INT_MAX
 #include <functional>
 #include <set>
 #include <type_traits>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_allocator.h"
 
 struct NotAnAllocator {
   friend bool operator<(NotAnAllocator, NotAnAllocator) { return false; }
 };
 
 int main(int, char **) {
   {
int main(int, char **) {
 
   {
     int source[3] = { 3, 4, 5 };
     std::set s{ source, source + 3 }; // set(initializer_list<int*>)
     ASSERT_SAME_TYPE(decltype(s), std::set<int *>);
     assert(s.size() == 2);
   }
 
+  AssociativeContainerDeductionGuidesSfinaeAway<std::set, std::set<int>>();
+
   return 0;
 }

libcxx/test/std/containers/container.adaptors/priority.queue/priqueue.cons/deduct.pass.cpp

 
 #include <queue>
 #include <vector>
 #include <iterator>
 #include <cassert>
 #include <cstddef>
 #include <climits> // INT_MAX
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "test_allocator.h"
 
 struct A {};
 
 int main(int, char**)
 {
assert(pri.size() == 0);
         {
         Cont cont;
         ConvertibleToT a[2] = {};
         std::priority_queue pri(a, a+2, Comp(), std::move(cont), ConvertibleToAlloc(2));
         static_assert(std::is_same_v<decltype(pri), std::priority_queue<T, Cont, Comp>>);
         }
     }
 
+    // Deduction guides should be SFINAE'd away when given:
+    // - "bad" input iterators (that is, a type not qualifying as an input
+    //   iterator);
+    // - a bad allocator;
+    // - an allocator instead of a comparator;
+    // - an allocator instead of a container;
+    // - an allocator and a container that uses a different allocator.
+    {
+        using Comp = std::less<int>;
+        using Cont = std::vector<int>;
+        using Alloc = std::allocator<int>;
+        using Iter = int*;
+
+        // The only requirement in the Standard is that integral types cannot be
+        // considered input iterators, beyond that it is unspecified.
+        using BadIter = int;
+#ifdef _LIBCPP_VERSION
+        struct OutputIter {
+          using iterator_category = std::output_iterator_tag;
+          using value_type = void;
+          using difference_type = void;
+          using pointer = void;
+          using reference = void;
+
+          const OutputIter& operator*() const { return *this; }
+          const OutputIter& operator++() { return *this; }
+          OutputIter operator++(int) const { return *this; }
+        };
+#endif // _LIBCPP_VERSION
+
+        struct BadAlloc {};
+        using AllocAsComp = Alloc;
+        using AllocAsCont = Alloc;
+        using DiffAlloc = test_allocator<int>;
+
+        // (iter, iter)
+        //
+        // Cannot deduce from (BAD_iter, BAD_iter)
+        static_assert(SFINAEs_away<std::priority_queue, BadIter, BadIter>);
+        // Note: (OutputIter, OutputIter) is interpreted as (comp, cont) and fails on accessing
+        // non-existent typedefs in `OutputIter` (as if it were a container). There is no
+        // requirement to SFINAE away bad containers.
+
+        // (iter, iter, comp)
+        //
+        // Cannot deduce from (BAD_iter, BAD_iter, comp)
+        static_assert(SFINAEs_away<std::priority_queue, BadIter, BadIter, Comp>);
+        LIBCPP_STATIC_ASSERT(SFINAEs_away<std::priority_queue, OutputIter, OutputIter, Comp>);
+        // Note: (iter, iter, ALLOC_as_comp) is allowed -- it just calls (iter, iter, alloc).
+
+        // (iter, iter, comp, cont)
+        //
+        // Cannot deduce from (BAD_iter, BAD_iter, comp, cont)
+        static_assert(SFINAEs_away<std::priority_queue, BadIter, BadIter, Comp, Cont>);
+        LIBCPP_STATIC_ASSERT(SFINAEs_away<std::priority_queue, OutputIter, OutputIter, Comp, Cont>);
+        // Cannot deduce from (iter, iter, ALLOC_as_comp, cont)
+        static_assert(SFINAEs_away<std::priority_queue, Iter, Iter, AllocAsComp, Cont>);
+        // Note: (iter, iter, comp, ALLOC_as_cont) is allowed -- it just calls (iter, iter, comp,
+        // alloc).
+
+        // (iter, iter, alloc)
+        //
+        // Cannot deduce from (BAD_iter, BAD_iter, alloc)
+        static_assert(SFINAEs_away<std::priority_queue, BadIter, BadIter, Alloc>);
+        LIBCPP_STATIC_ASSERT(SFINAEs_away<std::priority_queue, OutputIter, OutputIter, Alloc>);
+        // Note: (iter, iter, BAD_alloc) is interpreted as (iter, iter, comp) instead and fails upon
+        // instantiation. There is no requirement to SFINAE away bad comparators.
+
+        // (iter, iter, comp, alloc)
+        //
+        // Cannot deduce from (iter, iter, ALLOC_as_comp, alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Iter, Iter, AllocAsComp, Alloc>);
+        // Note: (iter, iter, comp, BAD_alloc) is interpreted as (iter, iter, comp, cont) instead
+        // and fails upon instantiation. There is no requirement to SFINAE away bad containers.
+
+        // (iter, iter, comp, cont, alloc)
+        //
+        // Cannot deduce from (BAD_iter, BAD_iter, comp, cont, alloc)
+        static_assert(SFINAEs_away<std::priority_queue, BadIter, BadIter, Comp, Cont, Alloc>);
+        LIBCPP_STATIC_ASSERT(
+            SFINAEs_away<std::priority_queue, OutputIter, OutputIter, Comp, Cont, Alloc>);
+        // Cannot deduce from (iter, iter, ALLOC_as_comp, cont, alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Iter, Iter, AllocAsComp, Cont, Alloc>);
+        // Cannot deduce from (iter, iter, comp, ALLOC_as_cont, alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Iter, Iter, Comp, AllocAsCont, Alloc>);
+        // Cannot deduce from (iter, iter, comp, cont, BAD_alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Iter, Iter, Comp, Cont, BadAlloc>);
+        // Cannot deduce from (iter, iter, comp, cont, DIFFERENT_alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Iter, Iter, Comp, Cont, DiffAlloc>);
+
+        // (comp, alloc)
+        //
+        // Cannot deduce from (ALLOC_as_comp, alloc)
+        static_assert(SFINAEs_away<std::priority_queue, AllocAsComp, Alloc>);
+        // Cannot deduce from (comp, BAD_alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Comp, BadAlloc>);
+
+        // (comp, cont, alloc)
+        //
+        // Cannot deduce from (ALLOC_as_comp, cont, alloc)
+        static_assert(SFINAEs_away<std::priority_queue, AllocAsComp, Cont, Alloc>);
+        // Cannot deduce from (comp, ALLOC_as_cont, alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Comp, AllocAsCont, Alloc>);
+        // Cannot deduce from (comp, cont, BAD_alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Comp, Cont, BadAlloc>);
+        // Cannot deduce from (comp, cont, DIFFERENT_alloc)
+        static_assert(SFINAEs_away<std::priority_queue, Comp, Cont, DiffAlloc>);
+
+        // (comp, cont)
+        //
+        // Cannot deduce from (ALLOC_as_comp, cont)
+        static_assert(SFINAEs_away<std::priority_queue, AllocAsComp, Cont>);
+        // Cannot deduce from (comp, ALLOC_as_cont)
+        static_assert(SFINAEs_away<std::priority_queue, Comp, AllocAsCont>);
+    }
+
     return 0;
 }

libcxx/test/std/containers/container.adaptors/queue/queue.cons/deduct.pass.cpp

 //   queue(Container, Allocator) -> queue<typename Container::value_type, Container>;
 
 
 #include <queue>
 #include <list>
 #include <iterator>
 #include <cassert>
 #include <cstddef>
-#include <climits> // INT_MAX
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "test_allocator.h"
 
 struct A {};
 
 int main(int, char**)
 {
assert(que.size() == 0);
 
         {
         std::queue<T, Cont> source;
         std::queue que(std::move(source), ConvertibleToAlloc(2));
         static_assert(std::is_same_v<decltype(que), std::queue<T, Cont>>);
         }
     }
 
+    // Deduction guides should be SFINAE'd away when given:
+    // - a "bad" allocator (that is, a type not qualifying as an allocator);
+    // - an allocator instead of a container;
+    // - an allocator and a container that uses a different allocator.
+    {
+        using Cont = std::list<int>;
+        using Alloc = std::allocator<int>;
+        using DiffAlloc = test_allocator<int>;
+
+        struct BadAlloc {};
+        using AllocAsCont = Alloc;
+
+        // (cont, alloc)
+        //
+        // Cannot deduce from (ALLOC_as_cont, alloc)
+        static_assert(SFINAEs_away<std::queue, AllocAsCont, BadAlloc>);
+        // Cannot deduce from (cont, BAD_alloc)
+        static_assert(SFINAEs_away<std::queue, Cont, BadAlloc>);
+        // Cannot deduce from (cont, DIFFERENT_alloc)
+        static_assert(SFINAEs_away<std::queue, Cont, DiffAlloc>);
+    }
+
     return 0;
 }

libcxx/test/std/containers/container.adaptors/stack/stack.cons/deduct.pass.cpp

 #include <deque>
 #include <vector>
 #include <list>
 #include <iterator>
 #include <cassert>
 #include <cstddef>
 #include <climits> // INT_MAX
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "test_allocator.h"
 
 struct A {};
 
 int main(int, char**)
 {
assert(stk.size() == 0);
 
         {
         std::stack<T, Cont> source;
         std::stack stk(std::move(source), ConvertibleToAlloc(2));
         static_assert(std::is_same_v<decltype(stk), std::stack<T, Cont>>);
         }
     }
 
+    // Deduction guides should be SFINAE'd away when given:
+    // - a "bad" allocator (that is, a type not qualifying as an allocator);
+    // - an allocator instead of a container;
+    // - an allocator and a container that uses a different allocator.
+    {
+        using Cont = std::list<int>;
+        using Alloc = std::allocator<int>;
+        using DiffAlloc = test_allocator<int>;
+
+        struct BadAlloc {};
+        using AllocAsCont = Alloc;
+
+        // (cont, alloc)
+        //
+        // Cannot deduce from (ALLOC_as_cont, alloc)
+        static_assert(SFINAEs_away<std::stack, AllocAsCont, Alloc>);
+        // Cannot deduce from (cont, BAD_alloc)
+        static_assert(SFINAEs_away<std::stack, Cont, BadAlloc>);
+        // Cannot deduce from (cont, DIFFERENT_alloc)
+        static_assert(SFINAEs_away<std::stack, Cont, DiffAlloc>);
+    }
+
     return 0;
 }

libcxx/test/std/containers/sequences/deque/deque.cons/deduct.pass.cpp

 //
 
 #include <deque>
 #include <iterator>
 #include <cassert>
 #include <cstddef>
 #include <climits> // INT_MAX
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "test_allocator.h"
 
 struct A {};
 
 int main(int, char**)
 {
assert(deq.size() == 0);
 
         {
         std::deque<short, Alloc> source;
         std::deque deq(std::move(source), ConvertibleToAlloc(2));
         static_assert(std::is_same_v<decltype(deq), decltype(source)>);
         }
     }
 
+    SequenceContainerDeductionGuidesSfinaeAway<std::deque, std::deque<int>>();
+
     return 0;
 }

libcxx/test/std/containers/sequences/forwardlist/forwardlist.cons/deduct.pass.cpp

 //
 
 #include <forward_list>
 #include <iterator>
 #include <cassert>
 #include <cstddef>
 #include <climits> // INT_MAX
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "test_allocator.h"
 
 struct A {};
 
 int main(int, char**)
 {
assert(std::distance(fwl.begin(), fwl.end()) == 0); // no size for forward_list
 
         {
         std::forward_list<short, Alloc> source;
         std::forward_list fwl(std::move(source), ConvertibleToAlloc(2));
         static_assert(std::is_same_v<decltype(fwl), decltype(source)>);
         }
     }
 
+    SequenceContainerDeductionGuidesSfinaeAway<std::forward_list, std::forward_list<int>>();
+
     return 0;
 }

libcxx/test/std/containers/sequences/list/list.cons/deduct.pass.cpp

 //
 
 #include <list>
 #include <iterator>
 #include <cassert>
 #include <cstddef>
 #include <climits> // INT_MAX
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "test_allocator.h"
 
 struct A {};
 
 int main(int, char**)
 {
assert(lst.size() == 0);
 
         {
         std::list<short, Alloc> source;
         std::list lst(std::move(source), ConvertibleToAlloc(2));
         static_assert(std::is_same_v<decltype(lst), decltype(source)>);
         }
     }
 
+    SequenceContainerDeductionGuidesSfinaeAway<std::list, std::list<int>>();
+
     return 0;
 }

libcxx/test/std/containers/sequences/vector/vector.cons/deduct.pass.cpp

 // UNSUPPORTED: c++03, c++11, c++14
 
 // template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
 //    vector(InputIterator, InputIterator, Allocator = Allocator())
 //    -> vector<typename iterator_traits<InputIterator>::value_type, Allocator>;
 //
 
 #include <vector>
-#include <iterator>
 #include <cassert>
 #include <cstddef>
 #include <climits> // INT_MAX
+#include <iterator>
+#include <type_traits>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "test_allocator.h"
 
 struct A {};
 
 int main(int, char**)
 {
assert(vec.size() == 0);
 
         {
         std::vector<short, Alloc> source;
         std::vector vec(std::move(source), ConvertibleToAlloc(2));
         static_assert(std::is_same_v<decltype(vec), decltype(source)>);
         }
     }
 
+    SequenceContainerDeductionGuidesSfinaeAway<std::vector, std::vector<int>>();
+
     return 0;
 }

libcxx/test/std/containers/unord/unord.map/unord.map.cnstr/deduct.pass.cpp

 //   -> unordered_map<Key, T, Hash, equal_to<Key>, Allocator>;
 
 #include <algorithm> // is_permutation
 #include <cassert>
 #include <climits> // INT_MAX
 #include <type_traits>
 #include <unordered_map>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_allocator.h"
 
 using P = std::pair<int, long>;
 using PC = std::pair<const int, long>;
 
 int main(int, char**)
 {
     const PC expected_m[] = { {1,1}, {2,2}, {3,1}, {INT_MAX,1} };
int main(int, char**)
     std::unordered_map m1{{std::pair{1, 2}, {3, 4}}, 0};
     ASSERT_SAME_TYPE(decltype(m1), std::unordered_map<int, int>);
 
     using value_type = std::pair<const int, int>;
     std::unordered_map m2{{value_type{1, 2}, {3, 4}}, 0};
     ASSERT_SAME_TYPE(decltype(m2), std::unordered_map<int, int>);
     }
 
+    UnorderedContainerDeductionGuidesSfinaeAway<std::unordered_map, std::unordered_map<int, long>>();
+
     return 0;
 }

libcxx/test/std/containers/unord/unord.multimap/unord.multimap.cnstr/deduct.pass.cpp

 //   -> unordered_multimap<Key, T, Hash, equal_to<Key>, Allocator>;
 
 #include <algorithm> // is_permutation
 #include <cassert>
 #include <climits> // INT_MAX
 #include <type_traits>
 #include <unordered_map>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_allocator.h"
 
 using P = std::pair<int, long>;
 using PC = std::pair<const int, long>;
 
 int main(int, char**)
 {
     const PC expected_m[] = { {1,1}, {1,1}, {2,2}, {3,1}, {INT_MAX,1} };
int main(int, char**)
     std::unordered_multimap m1{{std::pair{1, 2}, {3, 4}}, 0};
     ASSERT_SAME_TYPE(decltype(m1), std::unordered_multimap<int, int>);
 
     using value_type = std::pair<const int, int>;
     std::unordered_multimap m2{{value_type{1, 2}, {3, 4}}, 0};
     ASSERT_SAME_TYPE(decltype(m2), std::unordered_multimap<int, int>);
     }
 
+    UnorderedContainerDeductionGuidesSfinaeAway<std::unordered_multimap, std::unordered_multimap<int, long>>();
+
     return 0;
 }

libcxx/test/std/containers/unord/unord.multiset/unord.multiset.cnstr/deduct.pass.cpp

 //   -> unordered_multiset<T, Hash, equal_to<T>, Allocator>;
 
 #include <algorithm> // is_permutation
 #include <cassert>
 #include <climits> // INT_MAX
 #include <type_traits>
 #include <unordered_set>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_allocator.h"
 
 int main(int, char**)
 {
     const int expected_s[] = {1, 1, 2, 3, INT_MAX};
 
     {
     const int arr[] = { 1, 2, 1, INT_MAX, 3 };
int main(int, char**)
     {
     std::unordered_multiset s({ 1, 2, 1, INT_MAX, 3 }, 42, std::hash<long long>(), test_allocator<int>(0, 42));
 
     ASSERT_SAME_TYPE(decltype(s), std::unordered_multiset<int, std::hash<long long>, std::equal_to<int>, test_allocator<int>>);
     assert(std::is_permutation(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
     assert(s.get_allocator().get_id() == 42);
     }
 
+    UnorderedContainerDeductionGuidesSfinaeAway<std::unordered_multiset, std::unordered_multiset<int>>();
+
     return 0;
 }

libcxx/test/std/containers/unord/unord.set/unord.set.cnstr/deduct.pass.cpp

 //   -> unordered_set<T, Hash, equal_to<T>, Allocator>;
 
 #include <algorithm> // is_permutation
 #include <cassert>
 #include <climits> // INT_MAX
 #include <type_traits>
 #include <unordered_set>
 
+#include "deduction_guides_sfinae_checks.h"
 #include "test_allocator.h"
 
 int main(int, char**)
 {
     const int expected_s[] = {1, 2, 3, INT_MAX};
 
     {
     const int arr[] = { 1, 2, 1, INT_MAX, 3 };
int main(int, char**)
     {
     std::unordered_set s({ 1, 2, 1, INT_MAX, 3 }, 42, std::hash<long long>(), test_allocator<int>(0, 42));
 
     ASSERT_SAME_TYPE(decltype(s), std::unordered_set<int, std::hash<long long>, std::equal_to<int>, test_allocator<int>>);
     assert(std::is_permutation(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
     assert(s.get_allocator().get_id() == 42);
     }
 
+    UnorderedContainerDeductionGuidesSfinaeAway<std::unordered_set, std::unordered_set<int>>();
+
     return 0;
 }

libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/deduct.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <memory>
+
+// unique_ptr
+
+// The following constructors should not be selected by class template argument
+// deduction:
+//
+// explicit unique_ptr(pointer p)
+// unique_ptr(pointer p, const D& d) noexcept
+// unique_ptr(pointer p, remove_reference_t<D>&& d) noexcept
+
+#include <memory>
+
+#include "deduction_guides_sfinae_checks.h"
+
+struct Deleter {
+  void operator()(int* p) const { delete p; }
+};
+
+int main(int, char**) {
+  // Cannot deduce from (ptr).
+  static_assert(SFINAEs_away<std::unique_ptr, int*>);
+  // Cannot deduce from (array).
+  static_assert(SFINAEs_away<std::unique_ptr, int[]>);
+  // Cannot deduce from (ptr, Deleter&&).
+  static_assert(SFINAEs_away<std::unique_ptr, int*, Deleter&&>);
+  // Cannot deduce from (array, Deleter&&).
+  static_assert(SFINAEs_away<std::unique_ptr, int[], Deleter&&>);
+  // Cannot deduce from (ptr, const Deleter&).
+  static_assert(SFINAEs_away<std::unique_ptr, int*, const Deleter&>);
+  // Cannot deduce from (array, const Deleter&).
+  static_assert(SFINAEs_away<std::unique_ptr, int[], const Deleter&>);
+
+  return 0;
+}

libcxx/test/support/deduction_guides_sfinae_checks.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef TEST_SUPPORT_DEDUCTION_GUIDES_SFINAE_CHECKS_H
+#define TEST_SUPPORT_DEDUCTION_GUIDES_SFINAE_CHECKS_H
+
+#include <initializer_list>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+#include "test_macros.h"
+
+// `SFINAEs_away` template variable checks whether the template arguments for
+// a given template class `Instantiated` can be deduced from the given
+// constructor parameter types `CtrArgs` using CTAD.
+
+template<template<typename ...> class Instantiated, class ...CtrArgs,
+    class = decltype(Instantiated(std::declval<CtrArgs>()...))>
+std::false_type SFINAEs_away_impl(int);
+
+template<template<typename ...> class Instantiated, class ...CtrArgs>
+std::true_type SFINAEs_away_impl(...);
+
+template<template<typename ...> class Instantiated, class ...CtrArgs>
+constexpr bool SFINAEs_away =
+    decltype(SFINAEs_away_impl<Instantiated, CtrArgs...>(0))::value;
+
+// For sequence containers the deduction guides should be SFINAE'd away when
+// given:
+// - "bad" input iterators (that is, a type not qualifying as an input
+//   iterator);
+// - a bad allocator.
+template<template<typename ...> class Container, typename InstantiatedContainer>
+constexpr void SequenceContainerDeductionGuidesSfinaeAway() {
+  using Alloc = std::allocator<int>;
+  using Iter = int*;
+
+  struct BadAlloc {};
+  // Note: the only requirement in the Standard is that integral types cannot be
+  // considered input iterators; however, this doesn't work for sequence
+  // containers because they have constructors of the form `(size_type count,
+  // const value_type& value)`. These constructors would be used when passing
+  // two integral types and would deduce `value_type` to be an integral type.
+#ifdef _LIBCPP_VERSION
+  using OutputIter = std::insert_iterator<InstantiatedContainer>;
+#endif // _LIBCPP_VERSION
+
+  // (iter, iter)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter)
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter>);
+
+  // (iter, iter, alloc)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, alloc)
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter, Alloc>);
+  // Cannot deduce from (iter, iter, BAD_alloc)
+  static_assert(SFINAEs_away<Container, Iter, Iter, BadAlloc>);
+
+  // (alloc)
+  //
+  // Cannot deduce from (alloc)
+  static_assert(SFINAEs_away<Container, Alloc>);
+}
+
+// For associative containers the deduction guides should be SFINAE'd away when
+// given:
+// - "bad" input iterators (that is, a type not qualifying as an input
+//   iterator);
+// - a bad allocator;
+// - an allocator in place of a comparator.
+
+template<template<typename ...> class Container, typename InstantiatedContainer>
+constexpr void AssociativeContainerDeductionGuidesSfinaeAway() {
+  using ValueType = typename InstantiatedContainer::value_type;
+  using Comp = std::less<int>;
+  using Alloc = std::allocator<ValueType>;
+  using Iter = ValueType*;
+  using InitList = std::initializer_list<ValueType>;
+
+  struct BadAlloc {};
+  // The only requirement in the Standard is that integral types cannot be
+  // considered input iterators, beyond that it is unspecified.
+  using BadIter = int;
+#ifdef _LIBCPP_VERSION
+  using OutputIter = std::insert_iterator<InstantiatedContainer>;
+#endif // _LIBCPP_VERSION
+  using AllocAsComp = Alloc;
+
+  // (iter, iter)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter>);
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter>);
+
+  // (iter, iter, comp)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, comp)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, Comp>);
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter, Comp>);
+
+  // (iter, iter, comp, alloc)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, comp, alloc)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, Comp, Alloc>);
+  LIBCPP_STATIC_ASSERT(
+      SFINAEs_away<Container, OutputIter, OutputIter, Comp, Alloc>);
+  // Cannot deduce from (iter, iter, ALLOC_as_comp, alloc)
+  static_assert(SFINAEs_away<Container, Iter, Iter, AllocAsComp, Alloc>);
+  // Cannot deduce from (iter, iter, comp, BAD_alloc)
+  static_assert(SFINAEs_away<Container, Iter, Iter, Comp, BadAlloc>);
+
+  // (iter, iter, alloc)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, alloc)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, Alloc>);
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter, Alloc>);
+  // Note: (iter, iter, BAD_alloc) is interpreted as (iter, iter, comp)
+  // instead and fails upon instantiation. There is no requirement to SFINAE
+  // away bad comparators.
+
+  // (init_list, comp, alloc)
+  //
+  // Cannot deduce from (init_list, ALLOC_as_comp, alloc)
+  static_assert(SFINAEs_away<Container, InitList, AllocAsComp, Alloc>);
+  // Cannot deduce from (init_list, comp, BAD_alloc)
+  static_assert(SFINAEs_away<Container, InitList, Comp, BadAlloc>);
+
+  // (init_list, alloc)
+  //
+  // Note: (init_list, BAD_alloc) is interpreted as (init_list, comp) instead
+  // and fails upon instantiation. There is no requirement to SFINAE away bad
+  // comparators.
+}
+
+// For unordered containers the deduction guides should be SFINAE'd away when
+// given:
+// - "bad" input iterators (that is, a type not qualifying as an input
+//   iterator);
+// - a bad allocator;
+// - a bad hash functor (an integral type in place of a hash);
+// - an allocator in place of a hash functor;
+// - an allocator in place of a predicate.
+template<template<typename ...> class Container, typename InstantiatedContainer>
+constexpr void UnorderedContainerDeductionGuidesSfinaeAway() {
+  using ValueType = typename InstantiatedContainer::value_type;
+  using Pred = std::equal_to<int>;
+  using Hash = std::hash<int>;
+  using Alloc = std::allocator<ValueType>;
+  using Iter = ValueType*;
+  using InitList = std::initializer_list<ValueType>;
+
+  using BadHash = int;
+  struct BadAlloc {};
+  // The only requirement in the Standard is that integral types cannot be
+  // considered input iterators, beyond that it is unspecified.
+  using BadIter = int;
+#ifdef _LIBCPP_VERSION
+  using OutputIter = std::insert_iterator<InstantiatedContainer>;
+#endif // _LIBCPP_VERSION
+  using AllocAsHash = Alloc;
+  using AllocAsPred = Alloc;
+
+  // (iter, iter)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter>);
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter>);
+
+  // (iter, iter, buckets)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, buckets)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, size_t>);
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter, size_t>);
+
+  // (iter, iter, buckets, hash)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, buckets, hash)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, size_t, Hash>);
+  LIBCPP_STATIC_ASSERT(
+      SFINAEs_away<Container, OutputIter, OutputIter, size_t, Hash>);
+  // Cannot deduce from (iter, iter, buckets, BAD_hash)
+  static_assert(SFINAEs_away<Container, Iter, Iter, size_t, BadHash>);
+  // Note: (iter, iter, buckets, ALLOC_as_hash) is allowed -- it just calls
+  // (iter, iter, buckets, alloc)
+
+  // (iter, iter, buckets, hash, pred)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, buckets, hash, pred)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, size_t, Hash, Pred>);
+  LIBCPP_STATIC_ASSERT(
+      SFINAEs_away<Container, OutputIter, OutputIter, size_t, Hash, Pred>);
+  // Cannot deduce from (iter, iter, buckets, BAD_hash, pred)
+  static_assert(SFINAEs_away<Container, Iter, Iter, size_t, BadHash, Pred>);
+  // Cannot deduce from (iter, iter, buckets, ALLOC_as_hash, pred)
+  static_assert(SFINAEs_away<Container, Iter, Iter, size_t, AllocAsHash, Pred>);
+  // Note: (iter, iter, buckets, hash, ALLOC_as_pred) is allowed -- it just
+  // calls (iter, iter, buckets, hash, alloc)
+
+  // (iter, iter, buckets, hash, pred, alloc)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, buckets, hash, pred, alloc)
+  static_assert(
+      SFINAEs_away<Container, BadIter, BadIter, size_t, Hash, Pred, Alloc>);
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter,
+      size_t, Hash, Pred, Alloc>);
+  // Cannot deduce from (iter, iter, buckets, BAD_hash, pred, alloc)
+  static_assert(
+      SFINAEs_away<Container, Iter, Iter, size_t, BadHash, Pred, Alloc>);
+  // Cannot deduce from (iter, iter, buckets, ALLOC_as_hash, pred, alloc)
+  static_assert(
+      SFINAEs_away<Container, Iter, Iter, size_t, AllocAsHash, Pred, Alloc>);
+  // Cannot deduce from (iter, iter, buckets, hash, ALLOC_as_pred, alloc)
+  static_assert(
+      SFINAEs_away<Container, Iter, Iter, size_t, Hash, AllocAsPred, Alloc>);
+  // Cannot deduce from (iter, iter, buckets, hash, pred, BAD_alloc)
+  static_assert(
+      SFINAEs_away<Container, Iter, Iter, size_t, Hash, Pred, BadAlloc>);
+
+  // (iter, iter, buckets, alloc)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, buckets, alloc)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, size_t, Alloc>);
+  LIBCPP_STATIC_ASSERT(
+      SFINAEs_away<Container, OutputIter, OutputIter, size_t, Alloc>);
+  // Note: (iter, iter, buckets, BAD_alloc) is interpreted as (iter, iter,
+  // buckets, hash), which is valid because the only requirement for the hash
+  // parameter is that it's not integral.
+
+  // (iter, iter, alloc)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, alloc)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, Alloc>);
+  LIBCPP_STATIC_ASSERT(SFINAEs_away<Container, OutputIter, OutputIter, Alloc>);
+  // Cannot deduce from (iter, iter, BAD_alloc)
+  static_assert(SFINAEs_away<Container, Iter, Iter, BadAlloc>);
+
+  // (iter, iter, buckets, hash, alloc)
+  //
+  // Cannot deduce from (BAD_iter, BAD_iter, buckets, hash, alloc)
+  static_assert(SFINAEs_away<Container, BadIter, BadIter, size_t, Hash, Alloc>);
+  LIBCPP_STATIC_ASSERT(
+      SFINAEs_away<Container, OutputIter, OutputIter, size_t, Hash, Alloc>);
+  // Cannot deduce from (iter, iter, buckets, BAD_hash, alloc)
+  static_assert(SFINAEs_away<Container, Iter, Iter, size_t, BadHash, Alloc>);
+  // Cannot deduce from (iter, iter, buckets, ALLOC_as_hash, alloc)
+  static_assert(
+      SFINAEs_away<Container, Iter, Iter, size_t, AllocAsHash, Alloc>);
+  // Note: (iter, iter, buckets, hash, BAD_alloc) is interpreted as (iter, iter,
+  // buckets, hash, pred), which is valid because there are no requirements for
+  // the predicate.
+
+  // (init_list, buckets, hash)
+  //
+  // Cannot deduce from (init_list, buckets, BAD_hash)
+  static_assert(SFINAEs_away<Container, InitList, size_t, BadHash>);
+  // Note: (init_list, buckets, ALLOC_as_hash) is interpreted as (init_list,
+  // buckets, alloc), which is valid.
+
+  // (init_list, buckets, hash, pred)
+  //
+  // Cannot deduce from (init_list, buckets, BAD_hash, pred)
+  static_assert(SFINAEs_away<Container, InitList, size_t, BadHash, Pred>);
+  // Cannot deduce from (init_list, buckets, ALLOC_as_hash, pred)
+  static_assert(SFINAEs_away<Container, InitList, size_t, AllocAsHash, Pred>);
+  // Note: (init_list, buckets, hash, ALLOC_as_pred) is interpreted as
+  // (init_list, buckets, hash, alloc), which is valid.
+
+  // (init_list, buckets, hash, pred, alloc)
+  //
+  // Cannot deduce from (init_list, buckets, BAD_hash, pred, alloc)
+  static_assert(
+      SFINAEs_away<Container, InitList, size_t, BadHash, Pred, Alloc>);
+  // Cannot deduce from (init_list, buckets, ALLOC_as_hash, pred, alloc)
+  static_assert(
+      SFINAEs_away<Container, InitList, size_t, AllocAsHash, Pred, Alloc>);
+  // Cannot deduce from (init_list, buckets, hash, ALLOC_as_pred, alloc)
+  static_assert(
+      SFINAEs_away<Container, InitList, size_t, Hash, AllocAsPred, Alloc>);
+  // Cannot deduce from (init_list, buckets, hash, pred, BAD_alloc)
+  static_assert(
+      SFINAEs_away<Container, InitList, size_t, Hash, Pred, BadAlloc>);
+
+  // (init_list, buckets, alloc)
+  //
+  // Note: (init_list, buckets, BAD_alloc) is interpreted as (init_list,
+  // buckets, hash), which is valid because the only requirement for the hash
+  // parameter is that it's not integral.
+
+  // (init_list, buckets, hash, alloc)
+  //
+  // Cannot deduce from (init_list, buckets, BAD_hash, alloc)
+  static_assert(SFINAEs_away<Container, InitList, size_t, BadHash, Alloc>);
+  // Cannot deduce from (init_list, buckets, ALLOC_as_hash, alloc)
+  static_assert(SFINAEs_away<Container, InitList, size_t, AllocAsHash, Alloc>);
+
+  // (init_list, alloc)
+  //
+  // Cannot deduce from (init_list, BAD_alloc)
+  static_assert(SFINAEs_away<Container, InitList, BadAlloc>);
+}
+
+#endif // TEST_SUPPORT_DEDUCTION_GUIDES_SFINAE_CHECKS_H