From be8c7cd31c09bfef6cd3bb05b9ba00d2d6608d39 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Mon, 25 Sep 2023 14:45:17 -0700
Subject: [PATCH 1/5] Implement and test P1169R4 static operator()

---
 stl/inc/functional                            | 27 ++++++++-
 stl/inc/yvals_core.h                          |  1 +
 tests/std/test.lst                            |  1 +
 .../P1169R4_static_call_operator/env.lst      |  4 ++
 .../test.compile.pass.cpp                     | 55 +++++++++++++++++++
 5 files changed, 87 insertions(+), 1 deletion(-)
 create mode 100644 tests/std/tests/P1169R4_static_call_operator/env.lst
 create mode 100644 tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp

diff --git a/stl/inc/functional b/stl/inc/functional
index a0c97586e40..b5274c9f0b4 100644
--- a/stl/inc/functional
+++ b/stl/inc/functional
@@ -1139,12 +1139,37 @@ public:
 _NON_MEMBER_CALL(_FUNCTION_POINTER_DEDUCTION_GUIDE, X1, X2, X3)
 #undef _FUNCTION_POINTER_DEDUCTION_GUIDE
 
+template <class _Fx, class _Call_op, class = void>
+struct _Deduce_from_call_operator : _Is_memfunptr<_Call_op>::_Guide_type {}; // N4958 [func.wrap.func.con]/16.1
+
+#ifdef __cpp_static_call_operator // TRANSITION, P1169R4
+template <class>
+struct _Inspect_static_call_operator {};
+
+#define _STATIC_CALL_OPERATOR_GUIDES(CALL_OPT, CV_OPT, REF_OPT, NOEXCEPT_OPT)      \
+    template <class _Ret, class... _Args>                                          \
+    struct _Inspect_static_call_operator<_Ret(CALL_OPT*)(_Args...) NOEXCEPT_OPT> { \
+        using type = _Ret(_Args...);                                               \
+    };
+
+_NON_MEMBER_CALL(_STATIC_CALL_OPERATOR_GUIDES, , , )
+#ifdef __cpp_noexcept_function_type
+_NON_MEMBER_CALL(_STATIC_CALL_OPERATOR_GUIDES, , , noexcept)
+#endif // ^^^ defined(__cpp_noexcept_function_type) ^^^
+
+#undef _STATIC_CALL_OPERATOR_GUIDES
+
+template <class _Fx, class _Call_op>
+struct _Deduce_from_call_operator<_Fx, _Call_op, void_t<decltype(_STD declval<_Fx>().operator())>>
+    : _Inspect_static_call_operator<_Call_op> {}; // N4958 [func.wrap.func.con]/16.2
+#endif // ^^^ defined(__cpp_static_call_operator) ^^^
+
 template <class _Fx, class = void>
 struct _Deduce_signature {}; // can't deduce signature when &_Fx::operator() is missing, inaccessible, or ambiguous
 
 template <class _Fx>
 struct _Deduce_signature<_Fx, void_t<decltype(&_Fx::operator())>>
-    : _Is_memfunptr<decltype(&_Fx::operator())>::_Guide_type {}; // N4950 [func.wrap.func.con]/16.1
+    : _Deduce_from_call_operator<_Fx, decltype(&_Fx::operator())> {};
 
 template <class _Fx>
 function(_Fx) -> function<typename _Deduce_signature<_Fx>::type>;
diff --git a/stl/inc/yvals_core.h b/stl/inc/yvals_core.h
index e1df05934dd..19f28862251 100644
--- a/stl/inc/yvals_core.h
+++ b/stl/inc/yvals_core.h
@@ -328,6 +328,7 @@
 // P1072R10 basic_string::resize_and_overwrite
 // P1132R7 out_ptr(), inout_ptr()
 // P1147R1 Printing volatile Pointers
+// P1169R4 static operator()
 // P1206R7 Conversions From Ranges To Containers
 // P1223R5 ranges::find_last, ranges::find_last_if, ranges::find_last_if_not
 // P1272R4 byteswap()
diff --git a/tests/std/test.lst b/tests/std/test.lst
index 8c1a3602607..7b1396a5932 100644
--- a/tests/std/test.lst
+++ b/tests/std/test.lst
@@ -509,6 +509,7 @@ tests\P1135R6_latch
 tests\P1135R6_semaphore
 tests\P1147R1_printing_volatile_pointers
 tests\P1165R1_consistently_propagating_stateful_allocators
+tests\P1169R4_static_call_operator
 tests\P1206R7_deque_append_range
 tests\P1206R7_deque_assign_range
 tests\P1206R7_deque_from_range
diff --git a/tests/std/tests/P1169R4_static_call_operator/env.lst b/tests/std/tests/P1169R4_static_call_operator/env.lst
new file mode 100644
index 00000000000..642f530ffad
--- /dev/null
+++ b/tests/std/tests/P1169R4_static_call_operator/env.lst
@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_latest_matrix.lst
diff --git a/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp b/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp
new file mode 100644
index 00000000000..8d0607a8ebe
--- /dev/null
+++ b/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp
@@ -0,0 +1,55 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifdef __cpp_static_call_operator // TRANSITION, P1169R4
+
+#include <functional>
+#include <future>
+#include <type_traits>
+using namespace std;
+
+struct F0 {
+    static char operator()();
+};
+
+struct F1 {
+    static short operator()(float);
+};
+
+struct F2 {
+    static int operator()(double*, double&);
+};
+
+struct F3 {
+    static void operator()(const long&, long&&, const long&&);
+};
+
+struct Base {
+    static bool operator()(unsigned int);
+};
+
+struct Derived : Base {};
+
+struct Nothrow {
+    static char16_t operator()(char32_t) noexcept;
+};
+
+template <template <class> class Temp>
+void test_ctad() {
+    static_assert(is_same_v<decltype(Temp{F0{}}), Temp<char()>>);
+    static_assert(is_same_v<decltype(Temp{F1{}}), Temp<short(float)>>);
+    static_assert(is_same_v<decltype(Temp{F2{}}), Temp<int(double*, double&)>>);
+    static_assert(is_same_v<decltype(Temp{F3{}}), Temp<void(const long&, long&&, const long&&)>>);
+    static_assert(is_same_v<decltype(Temp{Derived{}}), Temp<bool(unsigned int)>>);
+    static_assert(is_same_v<decltype(Temp{Nothrow{}}), Temp<char16_t(char32_t)>>);
+
+    auto lambda = [](int* p, int** q) static { return *p + **q; };
+    static_assert(is_same_v<decltype(Temp{lambda}), Temp<int(int*, int**)>>);
+}
+
+void all_tests() {
+    test_ctad<function>();
+    test_ctad<packaged_task>();
+}
+
+#endif // ^^^ defined(__cpp_static_call_operator) ^^^

From be86c8693b28f23e0c34e2910bde069004e74817 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Mon, 25 Sep 2023 22:25:50 -0700
Subject: [PATCH 2/5] Clang backported this feature unconditionally.

---
 stl/inc/functional                                              | 2 +-
 .../tests/P1169R4_static_call_operator/test.compile.pass.cpp    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/stl/inc/functional b/stl/inc/functional
index b5274c9f0b4..8c0ce8f7944 100644
--- a/stl/inc/functional
+++ b/stl/inc/functional
@@ -1142,7 +1142,7 @@ _NON_MEMBER_CALL(_FUNCTION_POINTER_DEDUCTION_GUIDE, X1, X2, X3)
 template <class _Fx, class _Call_op, class = void>
 struct _Deduce_from_call_operator : _Is_memfunptr<_Call_op>::_Guide_type {}; // N4958 [func.wrap.func.con]/16.1
 
-#ifdef __cpp_static_call_operator // TRANSITION, P1169R4
+#ifdef __cpp_static_call_operator
 template <class>
 struct _Inspect_static_call_operator {};
 
diff --git a/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp b/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp
index 8d0607a8ebe..ecd82ea1de6 100644
--- a/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp
+++ b/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp
@@ -1,7 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-#ifdef __cpp_static_call_operator // TRANSITION, P1169R4
+#ifdef __cpp_static_call_operator
 
 #include <functional>
 #include <future>

From d1a63a790b4f24699e6d85a0642d8bbefcaa079e Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Mon, 25 Sep 2023 22:30:39 -0700
Subject: [PATCH 3/5] Update libcxx skips: these now pass for Clang.

---
 tests/libcxx/expected_results.txt | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/libcxx/expected_results.txt b/tests/libcxx/expected_results.txt
index 5efce3bf46a..07200dcb4a6 100644
--- a/tests/libcxx/expected_results.txt
+++ b/tests/libcxx/expected_results.txt
@@ -327,9 +327,6 @@ std/utilities/tuple/tuple.tuple/tuple.cnstr/recursion_depth.pass.cpp SKIPPED
 std/depr/depr.c.headers/uchar_h.compile.pass.cpp FAIL
 std/strings/c.strings/cuchar.compile.pass.cpp FAIL
 
-# P1169R4 static operator()
-std/thread/futures/futures.task/futures.task.members/ctad.static.compile.pass.cpp FAIL
-
 # P2255R2 "Type Traits To Detect References Binding To Temporaries"
 std/language.support/support.limits/support.limits.general/type_traits.version.compile.pass.cpp FAIL
 
@@ -349,6 +346,10 @@ std/utilities/format/format.tuple/set_separator.pass.cpp FAIL
 # MSVC doesn't properly support [[no_unique_address]]
 std/algorithms/algorithms.results/no_unique_address.compile.pass.cpp SKIPPED
 
+# P1169R4 static operator()
+std/thread/futures/futures.task/futures.task.members/ctad.static.compile.pass.cpp:0 FAIL
+std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/ctad.static.compile.pass.cpp:0 FAIL
+
 
 # *** MISSING LWG ISSUE RESOLUTIONS ***
 # LWG-2192 "Validity and return type of std::abs(0u) is unclear" (resolution is missing in UCRT, DevCom-10331466)
@@ -1065,7 +1066,6 @@ std/ranges/range.factories/range.single.view/cpo.pass.cpp FAIL
 std/thread/futures/futures.task/futures.task.members/ctor2.compile.pass.cpp FAIL
 std/utilities/format/format.functions/escaped_output.ascii.pass.cpp FAIL
 std/utilities/format/format.functions/locale-specific_form.pass.cpp FAIL
-std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/ctad.static.compile.pass.cpp FAIL
 std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.inv/invoke.pass.cpp:0 FAIL
 std/utilities/function.objects/refwrap/refwrap.const/type_conv_ctor.pass.cpp:0 FAIL
 std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/allocate_shared.array.unbounded.pass.cpp FAIL

From 135a6d1fa4ee64eeb5e36e0f9f1ac7ca30c08552 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Tue, 26 Sep 2023 08:43:01 -0700
Subject: [PATCH 4/5] Work around a Clang bug.

---
 .../tests/P1169R4_static_call_operator/test.compile.pass.cpp    | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp b/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp
index ecd82ea1de6..47b6bcd6374 100644
--- a/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp
+++ b/tests/std/tests/P1169R4_static_call_operator/test.compile.pass.cpp
@@ -43,8 +43,10 @@ void test_ctad() {
     static_assert(is_same_v<decltype(Temp{Derived{}}), Temp<bool(unsigned int)>>);
     static_assert(is_same_v<decltype(Temp{Nothrow{}}), Temp<char16_t(char32_t)>>);
 
+#if !(defined(__clang__) && defined(_M_IX86)) // TRANSITION, LLVM-62594, fixed in Clang 18
     auto lambda = [](int* p, int** q) static { return *p + **q; };
     static_assert(is_same_v<decltype(Temp{lambda}), Temp<int(int*, int**)>>);
+#endif // ^^^ no workaround ^^^
 }
 
 void all_tests() {

From 5ca381890531b0a55e3737b001072b77738d5e68 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Tue, 26 Sep 2023 16:13:30 -0700
Subject: [PATCH 5/5] Move the feature to the C++17 section.

---
 stl/inc/yvals_core.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stl/inc/yvals_core.h b/stl/inc/yvals_core.h
index 19f28862251..d3a4feed390 100644
--- a/stl/inc/yvals_core.h
+++ b/stl/inc/yvals_core.h
@@ -128,6 +128,7 @@
 // P0858R0 Constexpr Iterator Requirements
 // P1065R2 constexpr INVOKE
 //     (the std::invoke function only; other components like bind and reference_wrapper are C++20 only)
+// P1169R4 static operator()
 // P1518R2 Stop Overconstraining Allocators In Container Deduction Guides
 // P2162R2 Inheriting From variant
 // P2251R1 Require span And basic_string_view To Be Trivially Copyable
@@ -328,7 +329,6 @@
 // P1072R10 basic_string::resize_and_overwrite
 // P1132R7 out_ptr(), inout_ptr()
 // P1147R1 Printing volatile Pointers
-// P1169R4 static operator()
 // P1206R7 Conversions From Ranges To Containers
 // P1223R5 ranges::find_last, ranges::find_last_if, ranges::find_last_if_not
 // P1272R4 byteswap()