[PATCH] libstdc++: Remove non_type and replace it with constant_wrapper in function_ref
Jonathan Wakely
jwakely.gcc@gmail.com
Wed Apr 8 15:24:06 GMT 2026
On Wed, 8 Apr 2026, 13:56 Tomasz Kaminski, <tkaminsk@redhat.com> wrote:
> I have forgotten to bump function_ref FTM, but that turned out to be good
> thing, because we have another paper
> bumping it at the same time:
> https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3961r0.html
> Should we use 202304L for the second paper?
>
Yes that makes sense. Barry and I agree on behalf of sg10.
They seem separable, but we will inflict some order.
>
>
> On Wed, Apr 8, 2026 at 12:04 PM Jonathan Wakely <jwakely.gcc@gmail.com>
> wrote:
>
>>
>>
>> On Wed, 8 Apr 2026, 10:46 Tomasz Kamiński, <tkaminsk@redhat.com> wrote:
>>
>>> From: Matthias Kretz <m.kretz@gsi.de>
>>>
>>> This implements P3948R1: constant_wrapper is the only tool needed
>>> for passing constant expressions via function arguments.
>>>
>>> This changes function_ref from nontype_t to constant_wrapper and
>>> implements the ambiguity check (static_asert in function_ref
>>> from constant_wrapper constructor).
>>>
>>> In addition to P3948R1 this also includes the (forgotten) deduction
>>> guide changes suggested in the draft PR [1].
>>>
>>> [1] https://github.com/cplusplus/draft/pull/8878
>>>
>>> libstdc++-v3/ChangeLog:
>>>
>>> * include/bits/funcref_impl.h (function_ref::function_ref):
>>> Change nontype_t parameter to constant_wrapper, and adjust
>>> accordingly. Add static_assert detecting ambigous semantics.
>>> (function_refoperator=): Detect constant_wrapper rather than
>>> nontype_t.
>>>
>>
>> Missing :: here
>>
>> * include/bits/funcwrap.h (function_ref): Change
>>> * include/bits/utility.h (std::nontype_t, std::nontype)
>>> (std::__is_nontype_v): Remove.
>>> (_is_constant_wrapper_v): Define.
>>>
>>
>> And _ here
>>
>> The patch itself is fine, so OK with those two tweaks to the changelog.
>>
>>
>> * src/c++23/std.cc.in (std::nontype_t, std::nontype):
>>> Remove exports.
>>> * testsuite/20_util/function_ref/cw_cons_neg.cc: New tests
>>> for ambiguity check.
>>> * testsuite/20_util/function_ref/assign.cc: Replace nontype_t
>>> with constant_wrapper and nontype with std::cw.
>>> * testsuite/20_util/function_ref/call.cc: Likewise.
>>> * testsuite/20_util/function_ref/cons.cc: Likewise.
>>> * testsuite/20_util/function_ref/cons_neg.cc: Likewise.
>>> * testsuite/20_util/function_ref/deduction.cc: Likewise.
>>> * testsuite/20_util/function_ref/mutation.cc: Likewise.
>>>
>>> Co-authored-by: Tomasz Kamiński <tkaminsk@redhat.com>
>>> Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
>>> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
>>> ---
>>> This is based on Matthias patch from formge:
>>>
>>> https://forge.sourceware.org/gcc/gcc-TEST/pulls/147/commits/cac7355bcbd7ea8b5e26f064922e8f4412a4da97
>>>
>>> I have applied small adjustment to names and parameter specification,
>>> to be more consistient with the standard. Outside of that I have reworked
>>> static_assert to reflect more closely what is in the standard, and added
>>> negative test (cw_const_neg.cc).
>>>
>>> Testing on x86_64-linux. All *function_ref* test already passed in
>>> all standard modes and with modules. OK for trunk when all test passes?
>>>
>>>
>>> libstdc++-v3/include/bits/funcref_impl.h | 36 ++++----
>>> libstdc++-v3/include/bits/funcwrap.h | 13 +--
>>> libstdc++-v3/include/bits/utility.h | 23 ++---
>>> libstdc++-v3/src/c++23/std.cc.in | 4 -
>>> .../testsuite/20_util/function_ref/assign.cc | 27 +++---
>>> .../testsuite/20_util/function_ref/call.cc | 51 ++++++------
>>> .../testsuite/20_util/function_ref/cons.cc | 83 +++++++++----------
>>> .../20_util/function_ref/cons_neg.cc | 17 ++--
>>> .../20_util/function_ref/cw_cons_neg.cc | 35 ++++++++
>>> .../20_util/function_ref/dangling.cc | 2 +-
>>> .../20_util/function_ref/deduction.cc | 48 +++++------
>>> .../20_util/function_ref/mutation.cc | 9 +-
>>> 12 files changed, 185 insertions(+), 163 deletions(-)
>>> create mode 100644
>>> libstdc++-v3/testsuite/20_util/function_ref/cw_cons_neg.cc
>>>
>>> diff --git a/libstdc++-v3/include/bits/funcref_impl.h
>>> b/libstdc++-v3/include/bits/funcref_impl.h
>>> index 3d55c8406b0..9fcab570803 100644
>>> --- a/libstdc++-v3/include/bits/funcref_impl.h
>>> +++ b/libstdc++-v3/include/bits/funcref_impl.h
>>> @@ -129,12 +129,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>> // _GLIBCXX_RESOLVE_LIB_DEFECTS
>>> // 4256. Incorrect constrains for function_ref constructors from
>>> nontype
>>> /// Target object is __fn. There is no bound object.
>>> - template<auto __fn>
>>> - requires __is_invocable_using<const decltype(__fn)&>
>>> + template<auto __cwfn, typename _Fn>
>>> + requires __is_invocable_using<const _Fn&>
>>> constexpr
>>> - function_ref(nontype_t<__fn>) noexcept
>>> + function_ref(constant_wrapper<__cwfn, _Fn>) noexcept
>>> {
>>> - using _Fn = remove_cv_t<decltype(__fn)>;
>>> + constexpr const _Fn& __fn = constant_wrapper<__cwfn,
>>> _Fn>::value;
>>> + if constexpr (sizeof...(_ArgTypes) > 0)
>>> + if constexpr ((... &&
>>> _ConstExprParam<remove_cvref_t<_ArgTypes>>))
>>> + static_assert(!requires {
>>> + typename constant_wrapper<
>>> + std::__invoke(__fn,
>>> remove_cvref_t<_ArgTypes>::value...)>;
>>> + }, "cw<fn>(args...) should be equivalent to fn(args...)");
>>> +
>>> if constexpr (is_pointer_v<_Fn> || is_member_pointer_v<_Fn>)
>>> static_assert(__fn != nullptr);
>>>
>>> @@ -144,13 +151,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>>
>>> /// Target object is equivalent to
>>> std::bind_front<_fn>(std::ref(__ref)).
>>> /// Bound object is object referenced by second parameter.
>>> - template<auto __fn, typename _Up, typename _Td =
>>> remove_reference_t<_Up>>
>>> + template<auto __cwfn, typename _Fn, typename _Up,
>>> + typename _Td = remove_reference_t<_Up>>
>>> requires (!is_rvalue_reference_v<_Up&&>)
>>> - && __is_invocable_using<const decltype(__fn)&, _Td
>>> _GLIBCXX_MOF_CV&>
>>> + && __is_invocable_using<const _Fn&, _Td
>>> _GLIBCXX_MOF_CV&>
>>> constexpr
>>> - function_ref(nontype_t<__fn>, _Up&& __ref) noexcept
>>> + function_ref(constant_wrapper<__cwfn, _Fn>, _Up&& __ref) noexcept
>>> {
>>> - using _Fn = remove_cv_t<decltype(__fn)>;
>>> + constexpr const _Fn& __fn = constant_wrapper<__cwfn,
>>> _Fn>::value;
>>> if constexpr (is_pointer_v<_Fn> || is_member_pointer_v<_Fn>)
>>> static_assert(__fn != nullptr);
>>>
>>> @@ -166,12 +174,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>>
>>> /// Target object is equivalent to std::bind_front<_fn>(__ptr).
>>> /// Bound object is object pointed by second parameter (if any).
>>> - template<auto __fn, typename _Td>
>>> - requires __is_invocable_using<const decltype(__fn)&, _Td
>>> _GLIBCXX_MOF_CV*>
>>> + template< auto __cwfn, typename _Fn, typename _Td>
>>> + requires __is_invocable_using<const _Fn&, _Td _GLIBCXX_MOF_CV*>
>>> constexpr
>>> - function_ref(nontype_t<__fn>, _Td _GLIBCXX_MOF_CV* __ptr)
>>> noexcept
>>> + function_ref(constant_wrapper<__cwfn, _Fn>, _Td _GLIBCXX_MOF_CV*
>>> __ptr) noexcept
>>> {
>>> - using _Fn = remove_cv_t<decltype(__fn)>;
>>> + constexpr const _Fn& __fn = constant_wrapper<__cwfn,
>>> _Fn>::value;
>>> if constexpr (is_pointer_v<_Fn> || is_member_pointer_v<_Fn>)
>>> static_assert(__fn != nullptr);
>>> if constexpr (is_member_pointer_v<_Fn>)
>>> @@ -182,8 +190,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>> }
>>>
>>> template<typename _Tp>
>>> - requires (!is_same_v<_Tp, function_ref>)
>>> - && (!is_pointer_v<_Tp>) && (!__is_nontype_v<_Tp>)
>>> + requires (!is_same_v<_Tp, function_ref>) && (!is_pointer_v<_Tp>)
>>> + && (!__is_constant_wrapper_v<_Tp>)
>>> function_ref&
>>> operator=(_Tp) = delete;
>>>
>>> diff --git a/libstdc++-v3/include/bits/funcwrap.h
>>> b/libstdc++-v3/include/bits/funcwrap.h
>>> index 6441893d213..b835e075295 100644
>>> --- a/libstdc++-v3/include/bits/funcwrap.h
>>> +++ b/libstdc++-v3/include/bits/funcwrap.h
>>> @@ -573,15 +573,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>> requires is_function_v<_Fn>
>>> function_ref(_Fn*) -> function_ref<_Fn>;
>>>
>>> - template<auto __f, class _Fn = remove_pointer_t<decltype(__f)>>
>>> - requires is_function_v<_Fn>
>>> - function_ref(nontype_t<__f>) -> function_ref<_Fn>;
>>> + template<auto __cwfn, typename _Fn>
>>> + requires is_function_v<remove_pointer_t<_Fn>>
>>> + function_ref(constant_wrapper<__cwfn, _Fn>)
>>> + -> function_ref<remove_pointer_t<_Fn>>;
>>>
>>> - template<auto __f, typename _Tp,
>>> + template<auto __cwfn, typename _Fn, typename _Tp,
>>> typename _SignaturePtr =
>>> - decltype(__polyfunc::__deduce_funcref<decltype(__f),
>>> _Tp&>())>
>>> + decltype(__polyfunc::__deduce_funcref<_Fn, _Tp&>())>
>>> requires (!is_void_v<_SignaturePtr>)
>>> - function_ref(nontype_t<__f>, _Tp&&)
>>> + function_ref(constant_wrapper<__cwfn, _Fn>, _Tp&&)
>>> -> function_ref<remove_pointer_t<_SignaturePtr>>;
>>>
>>> #endif // __glibcxx_function_ref
>>> diff --git a/libstdc++-v3/include/bits/utility.h
>>> b/libstdc++-v3/include/bits/utility.h
>>> index 970e63e8170..93e9e9f9dba 100644
>>> --- a/libstdc++-v3/include/bits/utility.h
>>> +++ b/libstdc++-v3/include/bits/utility.h
>>> @@ -458,6 +458,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>> { return value; }
>>> };
>>>
>>> + template<typename>
>>> + constexpr bool __is_constant_wrapper_v = false;
>>> +
>>> + template<auto __cw, typename _Fn>
>>> + constexpr bool __is_constant_wrapper_v<constant_wrapper<__cw, _Fn>>
>>> = true;
>>> +
>>> template<_CwFixedValue _Tp>
>>> constexpr auto cw = constant_wrapper<_Tp>{};
>>> #endif
>>> @@ -637,23 +643,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>> inline constexpr sorted_equivalent_t sorted_equivalent{};
>>> #endif
>>>
>>> -#if __glibcxx_function_ref // >= C++26
>>> - template<auto>
>>> - struct nontype_t
>>> - {
>>> - explicit nontype_t() = default;
>>> - };
>>> -
>>> - template<auto __val>
>>> - constexpr nontype_t<__val> nontype{};
>>> -
>>> - template<typename>
>>> - inline constexpr bool __is_nontype_v = false;
>>> -
>>> - template<auto __val>
>>> - inline constexpr bool __is_nontype_v<nontype_t<__val>> = true;
>>> -#endif
>>> -
>>> _GLIBCXX_END_NAMESPACE_VERSION
>>> } // namespace
>>>
>>> diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/
>>> std.cc.in
>>> index db66677d55b..3ac19871692 100644
>>> --- a/libstdc++-v3/src/c++23/std.cc.in
>>> +++ b/libstdc++-v3/src/c++23/std.cc.in
>>> @@ -3651,10 +3651,6 @@ export namespace std
>>> using std::make_integer_sequence;
>>> using std::move;
>>> using std::move_if_noexcept;
>>> -#if __cpp_lib_function_ref
>>> - using std::nontype_t;
>>> - using std::nontype;
>>> -#endif
>>> using std::pair;
>>> using std::swap;
>>> using std::operator==;
>>> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/assign.cc
>>> b/libstdc++-v3/testsuite/20_util/function_ref/assign.cc
>>> index 9b02dc49c2a..521a35fc11e 100644
>>> --- a/libstdc++-v3/testsuite/20_util/function_ref/assign.cc
>>> +++ b/libstdc++-v3/testsuite/20_util/function_ref/assign.cc
>>> @@ -8,8 +8,7 @@
>>> # error "Feature-test macro for function_ref has wrong value in
>>> <functional>"
>>> #endif
>>>
>>> -using std::nontype;
>>> -using std::nontype_t;
>>> +using std::constant_wrapper;
>>> using std::function_ref;
>>>
>>> using std::is_nothrow_move_assignable_v;
>>> @@ -55,13 +54,13 @@ static_assert( !
>>> is_assignable_v<function_ref<int(S)>, decltype(&S::x)> );
>>> static_assert( ! is_assignable_v<function_ref<int(S)>, decltype(&S::f)>
>>> );
>>>
>>> static_assert( is_nothrow_assignable_v<function_ref<int(S)>,
>>> - nontype_t<funS>> );
>>> + constant_wrapper<funS>> );
>>> static_assert( is_nothrow_assignable_v<function_ref<int(S)>,
>>> - nontype_t<&funS>> );
>>> + constant_wrapper<&funS>> );
>>> static_assert( is_nothrow_assignable_v<function_ref<int(S)>,
>>> - nontype_t<&S::x>> );
>>> + constant_wrapper<&S::x>> );
>>> static_assert( is_nothrow_assignable_v<function_ref<int(S)>,
>>> - nontype_t<&S::f>> );
>>> + constant_wrapper<&S::f>> );
>>> struct Q
>>> {
>>> void operator()() const;
>>> @@ -75,22 +74,22 @@ static_assert( ! is_assignable_v<function_ref<void()
>>> const>, Q&> );
>>> static_assert( ! is_assignable_v<function_ref<void() const>, const Q&>
>>> );
>>>
>>> static_assert( is_nothrow_assignable_v<function_ref<void()>,
>>> - nontype_t<Q{}>> );
>>> + constant_wrapper<Q{}>> );
>>> static_assert( is_nothrow_assignable_v<function_ref<void() const>,
>>> - nontype_t<Q{}>> );
>>> + constant_wrapper<Q{}>> );
>>>
>>> constexpr bool
>>> test_constexpr()
>>> {
>>> - function_ref<void(S)> fp(nontype<funS>);
>>> - fp = nontype<funS>;
>>> - fp = nontype<&funS>;
>>> - fp = nontype<&S::x>;
>>> - fp = nontype<&S::f>;
>>> + function_ref<void(S)> fp(std::cw<funS>);
>>> + fp = std::cw<funS>;
>>> + fp = std::cw<&funS>;
>>> + fp = std::cw<&S::x>;
>>> + fp = std::cw<&S::f>;
>>>
>>> constexpr Q cq;
>>> function_ref<void() const> fq(cq);
>>> - fq = nontype<cq>;
>>> + fq = std::cw<cq>;
>>> return true;
>>> }
>>> static_assert( test_constexpr() );
>>> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/call.cc
>>> b/libstdc++-v3/testsuite/20_util/function_ref/call.cc
>>> index 49c6030b221..386c8de790a 100644
>>> --- a/libstdc++-v3/testsuite/20_util/function_ref/call.cc
>>> +++ b/libstdc++-v3/testsuite/20_util/function_ref/call.cc
>>> @@ -4,7 +4,6 @@
>>> #include <utility>
>>> #include <testsuite_hooks.h>
>>>
>>> -using std::nontype;
>>> using std::function_ref;
>>>
>>> using std::is_same_v;
>>> @@ -43,7 +42,7 @@ test01()
>>> VERIFY( f0() == 0 );
>>> VERIFY( std::move(f0)() == 0 );
>>>
>>> - function_ref<int()> f1{nontype<F{}>};
>>> + function_ref<int()> f1{std::cw<F{}>};
>>> VERIFY( f1() == 1 );
>>> VERIFY( std::move(f1)() == 1 );
>>>
>>> @@ -53,7 +52,7 @@ test01()
>>> VERIFY( std::move(f2)() == 1 );
>>> VERIFY( std::move(std::as_const(f2))() == 1 );
>>>
>>> - function_ref<int() const> f3{nontype<F{}>};
>>> + function_ref<int() const> f3{std::cw<F{}>};
>>> VERIFY( f3() == 1 );
>>> VERIFY( std::as_const(f3)() == 1 );
>>> VERIFY( std::move(f3)() == 1 );
>>> @@ -71,11 +70,11 @@ test02()
>>> };
>>> F::Arg arg;
>>>
>>> - function_ref<int()> f0{std::nontype<F{}>, arg};
>>> + function_ref<int()> f0{std::cw<F{}>, arg};
>>> VERIFY( f0() == 0 );
>>> VERIFY( std::move(f0)() == 0 );
>>>
>>> - function_ref<int() const> f1{std::nontype<F{}>, arg};
>>> + function_ref<int() const> f1{std::cw<F{}>, arg};
>>> VERIFY( f1() == 1 );
>>> VERIFY( std::as_const(f1)() == 1 );
>>> }
>>> @@ -91,11 +90,11 @@ test03()
>>> };
>>> F::Arg arg;
>>>
>>> - function_ref<int()> f0{std::nontype<F{}>, &arg};
>>> + function_ref<int()> f0{std::cw<F{}>, &arg};
>>> VERIFY( f0() == 0 );
>>> VERIFY( std::move(f0)() == 0 );
>>>
>>> - function_ref<int() const> f1{std::nontype<F{}>, &arg};
>>> + function_ref<int() const> f1{std::cw<F{}>, &arg};
>>> VERIFY( f1() == 1 );
>>> VERIFY( std::as_const(f1)() == 1 );
>>> }
>>> @@ -108,7 +107,7 @@ test04()
>>> VERIFY( f0() == 0 );
>>> VERIFY( std::move(f0)() == 0 );
>>>
>>> - function_ref<int()> f1{nontype<fp>};
>>> + function_ref<int()> f1{std::cw<fp>};
>>> VERIFY( f1() == 0 );
>>> VERIFY( std::move(f1)() == 0 );
>>>
>>> @@ -116,7 +115,7 @@ test04()
>>> VERIFY( f2() == 0 );
>>> VERIFY( std::move(f2)() == 0 );
>>>
>>> - const function_ref<int() const> f3{nontype<fp>};
>>> + const function_ref<int() const> f3{std::cw<fp>};
>>> VERIFY( f2() == 0 );
>>> VERIFY( std::move(f2)() == 0 );
>>> }
>>> @@ -130,14 +129,14 @@ int callback_ref(ftype& f, int x) { return f(x); }
>>> void
>>> test05()
>>> {
>>> - function_ref<int(int)> r1(nontype<&callback_ptr>, &twice);
>>> + function_ref<int(int)> r1(std::cw<&callback_ptr>, &twice);
>>> VERIFY( r1(2) == 4 );
>>> - function_ref<int(int)> r2(nontype<&callback_ptr>, cube);
>>> + function_ref<int(int)> r2(std::cw<&callback_ptr>, cube);
>>> VERIFY( r2(2) == 8 );
>>>
>>> - function_ref<int(int)> r3(nontype<&callback_ref>, twice);
>>> + function_ref<int(int)> r3(std::cw<&callback_ref>, twice);
>>> VERIFY( r3(3) == 6 );
>>> - function_ref<int(int)> r4(nontype<&callback_ref>, cube);
>>> + function_ref<int(int)> r4(std::cw<&callback_ref>, cube);
>>> VERIFY( r4(3) == 27 );
>>> }
>>>
>>> @@ -174,37 +173,37 @@ test06()
>>> std::function_ref<const int&(int, int) const> e8(std::as_const(csr));
>>> VERIFY( &e8(0, 0) == &s.v );
>>>
>>> - std::function_ref<int&()> f1(std::nontype<&S::v>, sr);
>>> + std::function_ref<int&()> f1(std::cw<&S::v>, sr);
>>> VERIFY( &f1() == &s.v );
>>> - std::function_ref<const int&()> f2(std::nontype<&S::v>, sr);
>>> + std::function_ref<const int&()> f2(std::cw<&S::v>, sr);
>>> VERIFY( &f2() == &s.v );
>>> - std::function_ref<int&()> f3(std::nontype<&S::m>, sr);
>>> + std::function_ref<int&()> f3(std::cw<&S::m>, sr);
>>> VERIFY( &f3() == &s.v );
>>> - std::function_ref<const int&()> f4(std::nontype<&S::c>, sr);
>>> + std::function_ref<const int&()> f4(std::cw<&S::c>, sr);
>>> VERIFY( &f4() == &s.v );
>>>
>>> - std::function_ref<const int&()> f5(std::nontype<&S::v>, csr);
>>> + std::function_ref<const int&()> f5(std::cw<&S::v>, csr);
>>> VERIFY( &f5() == &s.v );
>>> - std::function_ref<const int&()> f6(std::nontype<&S::c>, sr);
>>> + std::function_ref<const int&()> f6(std::cw<&S::c>, sr);
>>> VERIFY( &f6() == &s.v );
>>> static_assert( !std::is_constructible_v<
>>> std::function_ref<int&()>,
>>> - std::nontype_t<&S::c>, std::reference_wrapper<S>&>
>>> + std::constant_wrapper<&S::c>, std::reference_wrapper<S>&>
>>> );
>>>
>>> - std::function_ref<int&()> f7(std::nontype<&S::v>, std::as_const(sr));
>>> + std::function_ref<int&()> f7(std::cw<&S::v>, std::as_const(sr));
>>> VERIFY( &f7() == &s.v );
>>> - std::function_ref<const int&()> f8(std::nontype<&S::m>,
>>> std::as_const(sr));
>>> + std::function_ref<const int&()> f8(std::cw<&S::m>, std::as_const(sr));
>>> VERIFY( &f8() == &s.v );
>>>
>>> // No rvalue reference_wrapper support
>>> static_assert( !std::is_constructible_v<
>>> std::function_ref<int&()>,
>>> - std::nontype_t<&S::v>, std::reference_wrapper<S>>
>>> + std::constant_wrapper<&S::v>, std::reference_wrapper<S>>
>>> );
>>> static_assert( !std::is_constructible_v<
>>> std::function_ref<int&()>,
>>> - std::nontype_t<&S::v>, std::reference_wrapper<const S>>
>>> + std::constant_wrapper<&S::v>, std::reference_wrapper<const S>>
>>> );
>>>
>>> // reference to reference_wrapper are bound, so mutation are visible
>>> @@ -232,9 +231,9 @@ test06()
>>> { return &x; };
>>>
>>> // identity of reference_wrapper is preserved
>>> - std::function_ref<const std::reference_wrapper<S>*()>
>>> g1(std::nontype<id>, sr);
>>> + std::function_ref<const std::reference_wrapper<S>*()> g1(std::cw<id>,
>>> sr);
>>> VERIFY( g1() == &sr );
>>> - std::function_ref<const std::reference_wrapper<const S>*()>
>>> g2(std::nontype<id>, csr);
>>> + std::function_ref<const std::reference_wrapper<const S>*()>
>>> g2(std::cw<id>, csr);
>>> VERIFY( g2() == &csr );
>>> }
>>>
>>> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/cons.cc
>>> b/libstdc++-v3/testsuite/20_util/function_ref/cons.cc
>>> index a91f5ba3dab..78aebd38a07 100644
>>> --- a/libstdc++-v3/testsuite/20_util/function_ref/cons.cc
>>> +++ b/libstdc++-v3/testsuite/20_util/function_ref/cons.cc
>>> @@ -9,8 +9,7 @@
>>> # error "Feature-test macro for function_ref has wrong value in
>>> <functional>"
>>> #endif
>>>
>>> -using std::nontype;
>>> -using std::nontype_t;
>>> +using std::constant_wrapper;
>>> using std::function_ref;
>>>
>>> using std::is_default_constructible_v;
>>> @@ -60,31 +59,31 @@ static_assert( !
>>> is_constructible_v<function_ref<int(S)>,
>>> decltype(&S::f)> );
>>>
>>> static_assert( is_nothrow_constructible_v<function_ref<int(S)>,
>>> - nontype_t<funS>> );
>>> + constant_wrapper<funS>> );
>>> static_assert( is_nothrow_constructible_v<function_ref<int(S)>,
>>> - nontype_t<&funS>> );
>>> + constant_wrapper<&funS>> );
>>> static_assert( is_nothrow_constructible_v<function_ref<int(S)>,
>>> - nontype_t<&S::x>> );
>>> + constant_wrapper<&S::x>> );
>>> static_assert( is_nothrow_constructible_v<function_ref<int(S)>,
>>> - nontype_t<&S::f>> );
>>> + constant_wrapper<&S::f>> );
>>>
>>> static_assert( is_nothrow_constructible_v<function_ref<int()>,
>>> - nontype_t<funS>, S&> );
>>> + constant_wrapper<funS>, S&> );
>>> static_assert( is_nothrow_constructible_v<function_ref<int()>,
>>> - nontype_t<&funS>, S&> );
>>> + constant_wrapper<&funS>, S&> );
>>> static_assert( is_nothrow_constructible_v<function_ref<int()>,
>>> - nontype_t<&S::x>, S&> );
>>> + constant_wrapper<&S::x>, S&> );
>>> static_assert( is_nothrow_constructible_v<function_ref<int()>,
>>> - nontype_t<&S::f>, S&> );
>>> + constant_wrapper<&S::f>, S&> );
>>>
>>> static_assert( ! is_constructible_v<function_ref<int()>,
>>> - nontype_t<funS>, S*> );
>>> + constant_wrapper<funS>, S*> );
>>> static_assert( ! is_constructible_v<function_ref<int()>,
>>> - nontype_t<&funS>, S*> );
>>> + constant_wrapper<&funS>, S*> );
>>> static_assert( is_nothrow_constructible_v<function_ref<int()>,
>>> - nontype_t<&S::x>, S*> );
>>> + constant_wrapper<&S::x>, S*> );
>>> static_assert( is_nothrow_constructible_v<function_ref<int()>,
>>> - nontype_t<&S::f>, S*> );
>>> + constant_wrapper<&S::f>, S*> );
>>>
>>> struct M
>>> {
>>> @@ -98,9 +97,9 @@ static_assert( !
>>> is_constructible_v<function_ref<void()>, const M&> );
>>> static_assert( ! is_constructible_v<function_ref<void() const>, M> );
>>> static_assert( ! is_constructible_v<function_ref<void() const>, const
>>> M&> );
>>> static_assert( ! is_constructible_v<function_ref<void()>,
>>> - nontype_t<M{}>> );
>>> + constant_wrapper<M{}>> );
>>> static_assert( ! is_constructible_v<function_ref<void() const>,
>>> - nontype_t<M{}>> );
>>> + constant_wrapper<M{}>> );
>>> struct Q
>>> {
>>> void operator()(int) const;
>>> @@ -115,22 +114,22 @@ static_assert(
>>> is_nothrow_constructible_v<function_ref<void(int) const>, Q&> );
>>> static_assert( is_nothrow_constructible_v<function_ref<void(int)
>>> const>, const Q&> );
>>>
>>> static_assert( is_nothrow_constructible_v<function_ref<void(int)>,
>>> - nontype_t<Q{}>> );
>>> + constant_wrapper<Q{}>> );
>>> static_assert( is_nothrow_constructible_v<function_ref<void(int) const>,
>>> - nontype_t<Q{}>> );
>>> + constant_wrapper<Q{}>> );
>>> static_assert( is_nothrow_constructible_v<function_ref<void()>,
>>> - nontype_t<Q{}>, int&> );
>>> + constant_wrapper<Q{}>, int&> );
>>> static_assert( is_nothrow_constructible_v<function_ref<void() const>,
>>> - nontype_t<Q{}>, int&> );
>>> + constant_wrapper<Q{}>, int&> );
>>> static_assert( ! is_constructible_v<function_ref<void()>,
>>> - nontype_t<Q{}>, int> );
>>> + constant_wrapper<Q{}>, int> );
>>> static_assert( ! is_constructible_v<function_ref<void() const>,
>>> - nontype_t<Q{}>, int> );
>>> + constant_wrapper<Q{}>, int> );
>>>
>>> static_assert( is_nothrow_constructible_v<function_ref<void()>,
>>> - nontype_t<Q{}>, int*> );
>>> + constant_wrapper<Q{}>, int*> );
>>> static_assert( ! is_constructible_v<function_ref<void() const>,
>>> - nontype_t<Q{}>, int*> );
>>> + constant_wrapper<Q{}>, int*> );
>>>
>>> struct L
>>> {
>>> @@ -143,9 +142,9 @@ static_assert( !
>>> is_constructible_v<function_ref<void()>, const L&> );
>>> static_assert( ! is_constructible_v<function_ref<void() const>, L> );
>>> static_assert( ! is_constructible_v<function_ref<void() const>, const
>>> L&> );
>>> static_assert( ! is_constructible_v<function_ref<void()>,
>>> - nontype_t<L{}>> );
>>> + constant_wrapper<L{}>> );
>>> static_assert( ! is_constructible_v<function_ref<void() const>,
>>> - nontype_t<L{}>> );
>>> + constant_wrapper<L{}>> );
>>>
>>> struct R
>>> {
>>> @@ -159,24 +158,24 @@ static_assert( !
>>> is_constructible_v<function_ref<void(float) const>, R&> );
>>> static_assert( ! is_constructible_v<function_ref<void(float) const>,
>>> const R&> );
>>>
>>> static_assert( ! is_constructible_v<function_ref<void(float)>,
>>> - nontype_t<R{}>> );
>>> + constant_wrapper<R{}>> );
>>> static_assert( ! is_constructible_v<function_ref<void(float) const>,
>>> - nontype_t<R{}>> );
>>> + constant_wrapper<R{}>> );
>>>
>>> constexpr bool
>>> test_constexpr()
>>> {
>>> - function_ref<void(S)> fp1(nontype<funS>);
>>> - function_ref<void(S)> fp3(nontype<&funS>);
>>> - function_ref<void(S)> fp4(nontype<&S::x>);
>>> - function_ref<void(S)> fp5(nontype<&S::f>);
>>> + function_ref<void(S)> fp1(std::cw<funS>);
>>> + function_ref<void(S)> fp3(std::cw<&funS>);
>>> + function_ref<void(S)> fp4(std::cw<&S::x>);
>>> + function_ref<void(S)> fp5(std::cw<&S::f>);
>>>
>>> S s;
>>> - function_ref<void()> fp6(nontype<&funS>, s);
>>> - function_ref<void()> fp7(nontype<&S::x>, s);
>>> - function_ref<void()> fp8(nontype<&S::x>, &s);
>>> - function_ref<void()> fp9(nontype<&S::f>, s);
>>> - function_ref<void()> fp10(nontype<&S::f>, &s);
>>> + function_ref<void()> fp6(std::cw<&funS>, s);
>>> + function_ref<void()> fp7(std::cw<&S::x>, s);
>>> + function_ref<void()> fp8(std::cw<&S::x>, &s);
>>> + function_ref<void()> fp9(std::cw<&S::f>, s);
>>> + function_ref<void()> fp10(std::cw<&S::f>, &s);
>>>
>>> M m;
>>> function_ref<void()> fm1(m);
>>> @@ -190,13 +189,13 @@ test_constexpr()
>>>
>>> function_ref<void(int)> fcq1(cq);
>>> function_ref<void(int) const> f(cq);
>>> - function_ref<void(int)> fcq3(nontype<cq>);
>>> - function_ref<void(int) const> fcq4(nontype<cq>);
>>> + function_ref<void(int)> fcq3(std::cw<cq>);
>>> + function_ref<void(int) const> fcq4(std::cw<cq>);
>>>
>>> int i = 0;
>>> - function_ref<void()> fcq5(nontype<cq>, i);
>>> - function_ref<void() const> fcq6(nontype<cq>, i);
>>> - function_ref<void()> fcq7(nontype<cq>, &i);
>>> + function_ref<void()> fcq5(std::cw<cq>, i);
>>> + function_ref<void() const> fcq6(std::cw<cq>, i);
>>> + function_ref<void()> fcq7(std::cw<cq>, &i);
>>>
>>> L l;
>>> function_ref<void()> fl1(l);
>>> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/cons_neg.cc
>>> b/libstdc++-v3/testsuite/20_util/function_ref/cons_neg.cc
>>> index 050090df370..a426ac64cd5 100644
>>> --- a/libstdc++-v3/testsuite/20_util/function_ref/cons_neg.cc
>>> +++ b/libstdc++-v3/testsuite/20_util/function_ref/cons_neg.cc
>>> @@ -2,7 +2,6 @@
>>>
>>> #include <functional>
>>>
>>> -using std::nontype;
>>> using std::function_ref;
>>>
>>> struct S
>>> @@ -16,15 +15,15 @@ constexpr int(*fp)(S) = nullptr;
>>> constexpr int S::*mdp = nullptr;
>>> constexpr int (S::*mfp)() = nullptr;
>>>
>>> -function_ref<int(S)> fd1(nontype<fp>); // { dg-error "from here" }
>>> -function_ref<int(S)> fd2(nontype<mdp>); // { dg-error "from here" }
>>> -function_ref<int(S)> fd3(nontype<mfp>); // { dg-error "from here" }
>>> +function_ref<int(S)> fd1(std::cw<fp>); // { dg-error "from here" }
>>> +function_ref<int(S)> fd2(std::cw<mdp>); // { dg-error "from here" }
>>> +function_ref<int(S)> fd3(std::cw<mfp>); // { dg-error "from here" }
>>>
>>> -function_ref<int()> br4(nontype<fp>, s); // { dg-error "from here" }
>>> -function_ref<int()> br5(nontype<mdp>, s); // { dg-error "from here" }
>>> -function_ref<int()> br6(nontype<mfp>, s); // { dg-error "from here" }
>>> +function_ref<int()> br4(std::cw<fp>, s); // { dg-error "from here" }
>>> +function_ref<int()> br5(std::cw<mdp>, s); // { dg-error "from here" }
>>> +function_ref<int()> br6(std::cw<mfp>, s); // { dg-error "from here" }
>>>
>>> -function_ref<int()> bp7(nontype<mdp>, &s); // { dg-error "from here" }
>>> -function_ref<int()> bp8(nontype<mfp>, &s); // { dg-error "from here" }
>>> +function_ref<int()> bp7(std::cw<mdp>, &s); // { dg-error "from here" }
>>> +function_ref<int()> bp8(std::cw<mfp>, &s); // { dg-error "from here" }
>>>
>>> // { dg-prune-output "static assertion failed" }
>>> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/cw_cons_neg.cc
>>> b/libstdc++-v3/testsuite/20_util/function_ref/cw_cons_neg.cc
>>> new file mode 100644
>>> index 00000000000..a295bc2ce31
>>> --- /dev/null
>>> +++ b/libstdc++-v3/testsuite/20_util/function_ref/cw_cons_neg.cc
>>> @@ -0,0 +1,35 @@
>>> +// { dg-do compile { target c++26 } }
>>> +
>>> +#include <functional>
>>> +
>>> +using std::function_ref;
>>> +using std::constant_wrapper;
>>> +
>>> +struct S
>>> +{
>>> + int operator()() const { return 1; }
>>> +
>>> + // Non-constant, so cw<S{}>(cw<1>) call never unwrapps
>>> + int operator()(int) const { return 1; }
>>> + template<auto __cw>
>>> + int operator()(constant_wrapper<__cw, int>) const { return 1; }
>>> +
>>> + // Constant, cw<S{}>(cw<1>, cw<2>) calls int overload
>>> + // while S{}(cw<1>, cw<1>) calls constant_wrapper overload
>>> + constexpr int operator()(int, int) const { return 1; }
>>> + template<auto __cw1, auto __cw2>
>>> + constexpr int operator()(constant_wrapper<__cw1, int>,
>>> + constant_wrapper<__cw2, int>)
>>> + { return 1; }
>>> +};
>>> +
>>> +function_ref<int()> f0a(S{});
>>> +
>>> +function_ref<int(int)> f1a(S{});
>>> +function_ref<int(constant_wrapper<2>)> f1b(std::cw<S{}>);
>>> +
>>> +function_ref<int(int, int)> f2a(std::cw<S{}>); // OK, runtime
>>> +function_ref<int(constant_wrapper<1>, int)> f2b(std::cw<S{}>); // OK,
>>> still runtime
>>> +function_ref<int(constant_wrapper<2>, constant_wrapper<3>)>
>>> f2c(std::cw<S{}>); // { dg-error "from here" }
>>> +
>>> +// { dg-prune-output "static assertion failed" }
>>> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/dangling.cc
>>> b/libstdc++-v3/testsuite/20_util/function_ref/dangling.cc
>>> index 3cc782524f6..4ef5d067555 100644
>>> --- a/libstdc++-v3/testsuite/20_util/function_ref/dangling.cc
>>> +++ b/libstdc++-v3/testsuite/20_util/function_ref/dangling.cc
>>> @@ -46,7 +46,7 @@ struct NonStatic {
>>> { return x + y + v; }
>>> };
>>>
>>> -constexpr auto vNonType = create(std::nontype<NonStatic{3}>);
>>> +constexpr auto vNonType = create(std::cw<NonStatic{3}>);
>>>
>>> struct StaticWins {
>>> static int
>>> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/deduction.cc
>>> b/libstdc++-v3/testsuite/20_util/function_ref/deduction.cc
>>> index b034c7af072..63c3f6ea7e3 100644
>>> --- a/libstdc++-v3/testsuite/20_util/function_ref/deduction.cc
>>> +++ b/libstdc++-v3/testsuite/20_util/function_ref/deduction.cc
>>> @@ -4,15 +4,13 @@
>>> #include <type_traits>
>>>
>>> using std::is_same_v;
>>> -using std::nontype;
>>> -using std::nontype_t;
>>> using std::function_ref;
>>>
>>> int i = 0;
>>>
>>> template<auto f, class... Args>
>>> concept deductible = requires (Args&... args)
>>> - { std::function_ref(std::nontype<f>, args...); };
>>> + { std::function_ref(std::cw<f>, args...); };
>>>
>>> static_assert( !deductible<1> );
>>> static_assert( !deductible<1, int> );
>>> @@ -24,9 +22,9 @@ static_assert( is_same_v<decltype(function_ref(f0)),
>>> function_ref<void()>> );
>>> static_assert( is_same_v<decltype(function_ref(f0n)),
>>> function_ref<void() noexcept>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f0>)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f0>)),
>>> function_ref<void()>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f0n>)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f0n>)),
>>> function_ref<void() noexcept>> );
>>> static_assert( !deductible<f0, char*> );
>>> static_assert( !deductible<f0n, char*> );
>>> @@ -38,13 +36,13 @@ static_assert( is_same_v<decltype(function_ref(f1)),
>>> function_ref<void(int)>> );
>>> static_assert( is_same_v<decltype(function_ref(f1n)),
>>> function_ref<void(int) noexcept>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f1>)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f1>)),
>>> function_ref<void(int)>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f1n>)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f1n>)),
>>> function_ref<void(int) noexcept>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f1>, i)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f1>, i)),
>>> function_ref<void()>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f1n>, i)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f1n>, i)),
>>> function_ref<void() noexcept>> );
>>> static_assert( !deductible<f1, char*> );
>>> static_assert( !deductible<f1n, char*> );
>>> @@ -56,13 +54,13 @@ static_assert( is_same_v<decltype(function_ref(f2)),
>>> function_ref<void(int*, int)>> );
>>> static_assert( is_same_v<decltype(function_ref(f2n)),
>>> function_ref<void(int*, int) noexcept>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f2>)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f2>)),
>>> function_ref<void(int*, int)>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f2n>)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f2n>)),
>>> function_ref<void(int*, int) noexcept>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f2>, &i)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f2>, &i)),
>>> function_ref<void(int)>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<f2n>, &i)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<f2n>, &i)),
>>> function_ref<void(int) noexcept>> );
>>> static_assert( !deductible<f2, char*> );
>>> static_assert( !deductible<f2n, char*> );
>>> @@ -88,40 +86,40 @@ struct S
>>> S s{};
>>> const S cs{};
>>>
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::mem>, s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::mem>, s)),
>>> function_ref<int&() noexcept>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::mem>, cs)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::mem>, cs)),
>>> function_ref<const int&() noexcept>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::mem>, &s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::mem>, &s)),
>>> function_ref<int&() noexcept>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::mem>, &cs)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::mem>, &cs)),
>>> function_ref<const int&() noexcept>> );
>>> static_assert( !deductible<&S::mem, int> );
>>>
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::f>, s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::f>, s)),
>>> function_ref<int()>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::fn>, &s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::fn>, &s)),
>>> function_ref<int() noexcept>> );
>>> static_assert( !deductible<&S::f, char*> );
>>> static_assert( !deductible<&S::fn, char*> );
>>> static_assert( !deductible<&S::f, const S> );
>>> static_assert( !deductible<&S::fn, const S> );
>>>
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::fc>, &s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::fc>, &s)),
>>> function_ref<int(int)>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::fcn>, s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::fcn>, s)),
>>> function_ref<int(int) noexcept>> );
>>> static_assert( !deductible<&S::fc, char*> );
>>> static_assert( !deductible<&S::fcn, char*> );
>>>
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::fl>, &s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::fl>, &s)),
>>> function_ref<int(int)>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::fln>, s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::fln>, s)),
>>> function_ref<int(int) noexcept>> );
>>>
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::fcl>, s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::fcl>, s)),
>>> function_ref<int(float)>> );
>>> -static_assert( is_same_v<decltype(function_ref(nontype<&S::fcln>, &s)),
>>> +static_assert( is_same_v<decltype(function_ref(std::cw<&S::fcln>, &s)),
>>> function_ref<int(float) noexcept>> );
>>>
>>> static_assert( !deductible<&S::fr, char*> );
>>> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/mutation.cc
>>> b/libstdc++-v3/testsuite/20_util/function_ref/mutation.cc
>>> index 32c6931e9a8..d55f4facbda 100644
>>> --- a/libstdc++-v3/testsuite/20_util/function_ref/mutation.cc
>>> +++ b/libstdc++-v3/testsuite/20_util/function_ref/mutation.cc
>>> @@ -3,7 +3,6 @@
>>> #include <functional>
>>> #include <testsuite_hooks.h>
>>>
>>> -using std::nontype;
>>> using std::function_ref;
>>>
>>> void
>>> @@ -55,8 +54,8 @@ test02()
>>> };
>>> S s{10};
>>>
>>> - function_ref<int()> r1(nontype<&S::x>, s);
>>> - function_ref<long()> r2(nontype<&S::x>, &s);
>>> + function_ref<int()> r1(std::cw<&S::x>, s);
>>> + function_ref<long()> r2(std::cw<&S::x>, &s);
>>>
>>> VERIFY( r1() == 10 );
>>> VERIFY( r2() == 10 );
>>> @@ -66,8 +65,8 @@ test02()
>>> VERIFY( r1() == 20 );
>>> VERIFY( r2() == 20 );
>>>
>>> - r1 = function_ref<int()>(nontype<&S::f>, &s);
>>> - r2 = function_ref<long()>(nontype<&S::f>, s);
>>> + r1 = function_ref<int()>(std::cw<&S::f>, &s);
>>> + r2 = function_ref<long()>(std::cw<&S::f>, s);
>>>
>>> VERIFY( r1() == 20 );
>>> VERIFY( r2() == 20 );
>>> --
>>> 2.53.0
>>>
>>>
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