Add is_implicit_lifetime trait (for Clang)

stl/inc/type_traits

@@ -721,6 +721,14 @@ struct _NO_SPECIALIZATIONS_OF_TYPE_TRAITS is_trivially_copyable : bool_constant<
 _EXPORT_STD template <class _Ty>
 _NO_SPECIALIZATIONS_OF_TYPE_TRAITS constexpr bool is_trivially_copyable_v = __is_trivially_copyable(_Ty);
 
+#if _HAS_CXX23 && defined(__clang__) // TRANSITION, GH-5738 tracking VSO-2581622 (MSVC) and VSO-2581623 (EDG)
+_EXPORT_STD template <class _Ty>
+struct _NO_SPECIALIZATIONS_OF_TYPE_TRAITS is_implicit_lifetime : bool_constant<__builtin_is_implicit_lifetime(_Ty)> {};
+
+_EXPORT_STD template <class _Ty>
+_NO_SPECIALIZATIONS_OF_TYPE_TRAITS constexpr bool is_implicit_lifetime_v = __builtin_is_implicit_lifetime(_Ty);
+#endif // ^^^ _HAS_CXX23 && defined(__clang__) ^^^
+
 _EXPORT_STD template <class _Ty>
 struct _NO_SPECIALIZATIONS_OF_TYPE_TRAITS has_virtual_destructor : bool_constant<__has_virtual_destructor(_Ty)> {
     // determine whether _Ty has a virtual destructor

stl/inc/yvals_core.h

@@ -396,6 +396,7 @@
 // P2604R0 mdspan: data_handle_type, data_handle(), exhaustive
 // P2613R1 mdspan: empty()
 // P2652R2 Disallowing User Specialization Of allocator_traits
+// P2674R1 is_implicit_lifetime
 // P2693R1 Formatting thread::id And stacktrace
 // P2713R1 Escaping Improvements In std::format
 // P2763R1 Fixing layout_stride's Default Constructor For Fully Static Extents
@@ -1823,36 +1824,41 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
 #define __cpp_lib_generator                         202207L
 #define __cpp_lib_invoke_r                          202106L
 #define __cpp_lib_ios_noreplace                     202207L
-#define __cpp_lib_is_scoped_enum                    202011L
-#define __cpp_lib_mdspan                            202207L
-#define __cpp_lib_move_only_function                202110L
-#define __cpp_lib_out_ptr                           202311L
-#define __cpp_lib_print                             202406L
-#define __cpp_lib_ranges_as_const                   202311L
-#define __cpp_lib_ranges_as_rvalue                  202207L
-#define __cpp_lib_ranges_cartesian_product          202207L
-#define __cpp_lib_ranges_chunk                      202202L
-#define __cpp_lib_ranges_chunk_by                   202202L
-#define __cpp_lib_ranges_contains                   202207L
-#define __cpp_lib_ranges_enumerate                  202302L
-#define __cpp_lib_ranges_find_last                  202207L
-#define __cpp_lib_ranges_fold                       202207L
-#define __cpp_lib_ranges_iota                       202202L
-#define __cpp_lib_ranges_join_with                  202202L
-#define __cpp_lib_ranges_repeat                     202207L
-#define __cpp_lib_ranges_slide                      202202L
-#define __cpp_lib_ranges_starts_ends_with           202106L
-#define __cpp_lib_ranges_stride                     202207L
-#define __cpp_lib_ranges_to_container               202202L
-#define __cpp_lib_ranges_zip                        202110L
-#define __cpp_lib_spanstream                        202106L
-#define __cpp_lib_stacktrace                        202011L
-#define __cpp_lib_stdatomic_h                       202011L
-#define __cpp_lib_string_contains                   202011L
-#define __cpp_lib_string_resize_and_overwrite       202110L
-#define __cpp_lib_to_underlying                     202102L
-#define __cpp_lib_tuple_like                        202207L
-#define __cpp_lib_unreachable                       202202L
+
+#ifdef __clang__ // TRANSITION, GH-5738 tracking VSO-2581622 (MSVC) and VSO-2581623 (EDG)
+#define __cpp_lib_is_implicit_lifetime 202302L
+#endif // ^^^ no workaround ^^^
+
+#define __cpp_lib_is_scoped_enum              202011L
+#define __cpp_lib_mdspan                      202207L
+#define __cpp_lib_move_only_function          202110L
+#define __cpp_lib_out_ptr                     202311L
+#define __cpp_lib_print                       202406L
+#define __cpp_lib_ranges_as_const             202311L
+#define __cpp_lib_ranges_as_rvalue            202207L
+#define __cpp_lib_ranges_cartesian_product    202207L
+#define __cpp_lib_ranges_chunk                202202L
+#define __cpp_lib_ranges_chunk_by             202202L
+#define __cpp_lib_ranges_contains             202207L
+#define __cpp_lib_ranges_enumerate            202302L
+#define __cpp_lib_ranges_find_last            202207L
+#define __cpp_lib_ranges_fold                 202207L
+#define __cpp_lib_ranges_iota                 202202L
+#define __cpp_lib_ranges_join_with            202202L
+#define __cpp_lib_ranges_repeat               202207L
+#define __cpp_lib_ranges_slide                202202L
+#define __cpp_lib_ranges_starts_ends_with     202106L
+#define __cpp_lib_ranges_stride               202207L
+#define __cpp_lib_ranges_to_container         202202L
+#define __cpp_lib_ranges_zip                  202110L
+#define __cpp_lib_spanstream                  202106L
+#define __cpp_lib_stacktrace                  202011L
+#define __cpp_lib_stdatomic_h                 202011L
+#define __cpp_lib_string_contains             202011L
+#define __cpp_lib_string_resize_and_overwrite 202110L
+#define __cpp_lib_to_underlying               202102L
+#define __cpp_lib_tuple_like                  202207L
+#define __cpp_lib_unreachable                 202202L
 #endif // _HAS_CXX23
 
 // macros with language mode sensitivity

tests/libcxx/expected_results.txt

@@ -61,6 +61,9 @@ std/language.support/support.exception/except.nested/ctor_default.pass.cpp:2 SKI
 # SKIPPED because this is ARM64EC-specific.
 std/language.support/support.coroutines/coroutine.handle/coroutine.handle.noop/noop_coroutine.pass.cpp:2 SKIPPED
 
+# LLVM-160627: [libc++][test] Guard non-guaranteed implicit-lifetime-ness cases with _LIBCPP_VERSION
+std/utilities/meta/meta.unary/meta.unary.prop/is_implicit_lifetime.pass.cpp:2 FAIL
+
 # Non-Standard regex behavior.
 # "It seems likely that the test is still non-conforming due to how libc++ handles the 'w' character class."
 std/re/re.traits/lookup_classname.pass.cpp FAIL
@@ -565,9 +568,6 @@ std/utilities/meta/meta.unary/meta.unary.prop/reference_converts_from_temporary.
 std/utilities/tuple/tuple.tuple/tuple.cnstr/PR20855_tuple_ref_binding_diagnostics.pass.cpp:0 FAIL
 std/utilities/tuple/tuple.tuple/tuple.cnstr/PR20855_tuple_ref_binding_diagnostics.pass.cpp:1 FAIL
 
-# P2674R1 is_implicit_lifetime
-std/utilities/meta/meta.unary/meta.unary.prop/is_implicit_lifetime.pass.cpp FAIL
-
 # P2944R3 Comparisons For reference_wrapper
 # Add 'std-at-least-c++26' to tests/utils/stl/test/tests.py when beginning work on C++26.
 std/utilities/function.objects/refwrap/refwrap.comparisons/compare.three_way.refwrap.const_ref.pass.cpp FAIL
@@ -583,7 +583,9 @@ std/utilities/optional/optional.iterator/iterator.pass.cpp FAIL
 
 # *** MISSING COMPILER FEATURES ***
 
-# None!
+# VSO-2581622 C1XX should implement `__builtin_is_implicit_lifetime`
+std/utilities/meta/meta.unary/meta.unary.prop/is_implicit_lifetime.pass.cpp:0 FAIL
+std/utilities/meta/meta.unary/meta.unary.prop/is_implicit_lifetime.pass.cpp:1 FAIL
 
 
 # *** MISSING LWG ISSUE RESOLUTIONS ***

tests/std/test.lst

@@ -707,6 +707,7 @@ tests\P2510R3_text_formatting_pointers
 tests\P2517R1_apply_conditional_noexcept
 tests\P2538R1_adl_proof_std_projected
 tests\P2609R3_relaxing_ranges_just_a_smidge
+tests\P2674R1_is_implicit_lifetime
 tests\P2693R1_ostream_and_thread_id
 tests\P2693R1_text_formatting_header_stacktrace
 tests\P2693R1_text_formatting_header_thread

tests/std/tests/P2674R1_is_implicit_lifetime/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

tests/std/tests/P2674R1_is_implicit_lifetime/test.compile.pass.cpp

@@ -0,0 +1,180 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <cstddef>
+#include <string>
+#include <type_traits>
+using namespace std;
+
+enum UnscopedEnum { Enumerator };
+enum class ScopedEnum { Enumerator2 };
+class IncompleteClass;
+struct TrivialClass {};
+struct DefaultedDestructorClass {
+    ~DefaultedDestructorClass() = default;
+};
+struct DeletedDestructorClass {
+    ~DeletedDestructorClass() = delete;
+};
+struct UserProvidedDestructorClass {
+    ~UserProvidedDestructorClass() {}
+};
+struct StringAggregateWithImplicitlyDeclaredDestructor {
+    string juliette_andromeda_meow;
+    string clarissa_melpomene_meow;
+};
+struct StringAggregateWithUserProvidedDestructor {
+    string chaos_engine_one;
+    string chaos_engine_two;
+    ~StringAggregateWithUserProvidedDestructor() {}
+};
+
+class NonAggregateWithTrivialCtorAndTrivialDtor {
+public:
+    NonAggregateWithTrivialCtorAndTrivialDtor()  = default;
+    ~NonAggregateWithTrivialCtorAndTrivialDtor() = default;
+
+    NonAggregateWithTrivialCtorAndTrivialDtor(const NonAggregateWithTrivialCtorAndTrivialDtor&)            = delete;
+    NonAggregateWithTrivialCtorAndTrivialDtor& operator=(const NonAggregateWithTrivialCtorAndTrivialDtor&) = delete;
+
+    void set_num(int x) {
+        num = x;
+    }
+    int get_num() const {
+        return num;
+    }
+
+private:
+    int num;
+};
+
+class NonAggregateWithNonTrivialCtor {
+public:
+    NonAggregateWithNonTrivialCtor()  = default;
+    ~NonAggregateWithNonTrivialCtor() = default;
+
+    NonAggregateWithNonTrivialCtor(const NonAggregateWithNonTrivialCtor&)            = delete;
+    NonAggregateWithNonTrivialCtor& operator=(const NonAggregateWithNonTrivialCtor&) = delete;
+
+    void set_num(int x) {
+        num = x;
+    }
+    int get_num() const {
+        return num;
+    }
+
+private:
+    int num{0}; // default member initializer => non-trivial default constructor, N5014 [class.default.ctor]/3.2
+};
+
+class NonAggregateWithUserProvidedCtor {
+public:
+    NonAggregateWithUserProvidedCtor() {}
+    ~NonAggregateWithUserProvidedCtor() = default;
+
+    NonAggregateWithUserProvidedCtor(const NonAggregateWithUserProvidedCtor&)            = delete;
+    NonAggregateWithUserProvidedCtor& operator=(const NonAggregateWithUserProvidedCtor&) = delete;
+
+    void set_num(int x) {
+        num = x;
+    }
+    int get_num() const {
+        return num;
+    }
+
+private:
+    int num;
+};
+
+class NonAggregateWithDeletedDtor {
+public:
+    NonAggregateWithDeletedDtor()  = default;
+    ~NonAggregateWithDeletedDtor() = delete;
+
+    NonAggregateWithDeletedDtor(const NonAggregateWithDeletedDtor&)            = delete;
+    NonAggregateWithDeletedDtor& operator=(const NonAggregateWithDeletedDtor&) = delete;
+
+    void set_num(int x) {
+        num = x;
+    }
+    int get_num() const {
+        return num;
+    }
+
+private:
+    int num;
+};
+
+class NonAggregateWithUserProvidedDtor {
+public:
+    NonAggregateWithUserProvidedDtor() = default;
+    ~NonAggregateWithUserProvidedDtor() {}
+
+    NonAggregateWithUserProvidedDtor(const NonAggregateWithUserProvidedDtor&)            = delete;
+    NonAggregateWithUserProvidedDtor& operator=(const NonAggregateWithUserProvidedDtor&) = delete;
+
+    void set_num(int x) {
+        num = x;
+    }
+    int get_num() const {
+        return num;
+    }
+
+private:
+    int num;
+};
+
+#ifdef __cpp_lib_is_implicit_lifetime
+template <bool Val, typename T>
+constexpr bool test_implicit_lifetime = is_implicit_lifetime_v<T> == Val && is_implicit_lifetime<T>::value == Val;
+template <bool Val, typename T>
+constexpr bool test_implicit_lifetime_cv = test_implicit_lifetime<Val, T> //
+                                        && test_implicit_lifetime<Val, const T> //
+                                        && test_implicit_lifetime<Val, volatile T> //
+                                        && test_implicit_lifetime<Val, const volatile T>;
+
+// Scalar types, N5014 [basic.types.general]/9
+static_assert(test_implicit_lifetime_cv<true, int>);
+static_assert(test_implicit_lifetime_cv<true, UnscopedEnum>);
+static_assert(test_implicit_lifetime_cv<true, ScopedEnum>);
+static_assert(test_implicit_lifetime_cv<true, void*>);
+static_assert(test_implicit_lifetime_cv<true, int*>);
+static_assert(test_implicit_lifetime_cv<true, void (*)()>);
+static_assert(test_implicit_lifetime_cv<true, int TrivialClass::*>);
+static_assert(test_implicit_lifetime_cv<true, int (TrivialClass::*)(int)>);
+static_assert(test_implicit_lifetime_cv<true, nullptr_t>);
+
+// Implicit-lifetime class types, N5014 [class.prop]/16:
+// "A class S is an implicit-lifetime class if
+// - it is an aggregate whose destructor is not user-provided or
+// - it has at least one trivial eligible constructor and a trivial, non-deleted destructor."
+static_assert(test_implicit_lifetime_cv<true, TrivialClass>);
+static_assert(test_implicit_lifetime_cv<true, DefaultedDestructorClass>);
+static_assert(test_implicit_lifetime_cv<true, DeletedDestructorClass>);
+static_assert(test_implicit_lifetime_cv<false, UserProvidedDestructorClass>);
+static_assert(test_implicit_lifetime_cv<true, StringAggregateWithImplicitlyDeclaredDestructor>);
+static_assert(test_implicit_lifetime_cv<false, StringAggregateWithUserProvidedDestructor>);
+static_assert(test_implicit_lifetime_cv<true, NonAggregateWithTrivialCtorAndTrivialDtor>);
+#ifndef __clang__ // TRANSITION, LLVM-160610
+static_assert(test_implicit_lifetime_cv<false, NonAggregateWithNonTrivialCtor>);
+static_assert(test_implicit_lifetime_cv<false, NonAggregateWithUserProvidedCtor>);
+#endif // ^^^ no workaround ^^^
+static_assert(test_implicit_lifetime_cv<false, NonAggregateWithDeletedDtor>);
+static_assert(test_implicit_lifetime_cv<false, NonAggregateWithUserProvidedDtor>);
+
+// Arrays
+static_assert(test_implicit_lifetime_cv<true, int[]>);
+static_assert(test_implicit_lifetime_cv<true, int[2]>);
+static_assert(test_implicit_lifetime_cv<true, TrivialClass[]>);
+static_assert(test_implicit_lifetime_cv<true, TrivialClass[10]>);
+static_assert(test_implicit_lifetime_cv<true, UserProvidedDestructorClass[]>);
+static_assert(test_implicit_lifetime_cv<true, UserProvidedDestructorClass[12]>);
+static_assert(test_implicit_lifetime_cv<true, IncompleteClass[]>);
+static_assert(test_implicit_lifetime_cv<true, IncompleteClass[20]>);
+
+static_assert(test_implicit_lifetime_cv<false, void>);
+static_assert(test_implicit_lifetime<false, long&>);
+static_assert(test_implicit_lifetime<false, long&&>);
+static_assert(test_implicit_lifetime<false, const long&>);
+static_assert(test_implicit_lifetime<false, const long&&>);
+#endif // ^^^ defined(__cpp_lib_is_implicit_lifetime) ^^^

tests/std/tests/VSO_0157762_feature_test_macros/test.compile.pass.cpp

@@ -545,6 +545,12 @@ STATIC_ASSERT(__cpp_lib_is_constant_evaluated == 201811L);
 
 STATIC_ASSERT(__cpp_lib_is_final == 201402L);
 
+#if _HAS_CXX23 && defined(__clang__) // TRANSITION, GH-5738 tracking VSO-2581622 (MSVC) and VSO-2581623 (EDG)
+STATIC_ASSERT(__cpp_lib_is_implicit_lifetime == 202302L);
+#elif defined(__cpp_lib_is_implicit_lifetime)
+#error __cpp_lib_is_implicit_lifetime is defined
+#endif
+
 #if _HAS_CXX17
 STATIC_ASSERT(__cpp_lib_is_invocable == 201703L);
 #elif defined(__cpp_lib_is_invocable)