Fix truncation warnings in conjunction/disjunction (#4846)

stl/inc/type_traits

@@ -37,14 +37,14 @@ struct _Conjunction { // handle false trait or last trait
 
 template <class _True, class _Next, class... _Rest>
 struct _Conjunction<true, _True, _Next, _Rest...> { // the first trait is true, try the next one
-    using type = typename _Conjunction<_Next::value, _Next, _Rest...>::type;
+    using type = typename _Conjunction<static_cast<bool>(_Next::value), _Next, _Rest...>::type;
 };
 
 _EXPORT_STD template <class... _Traits>
 struct conjunction : true_type {}; // If _Traits is empty, true_type
 
 template <class _First, class... _Rest>
-struct conjunction<_First, _Rest...> : _Conjunction<_First::value, _First, _Rest...>::type {
+struct conjunction<_First, _Rest...> : _Conjunction<static_cast<bool>(_First::value), _First, _Rest...>::type {
     // the first false trait in _Traits, or the last trait if none are false
 };
 

stl/inc/xtr1common

@@ -152,14 +152,14 @@ struct _Disjunction { // handle true trait or last trait
 
 template <class _False, class _Next, class... _Rest>
 struct _Disjunction<false, _False, _Next, _Rest...> { // first trait is false, try the next trait
-    using type = typename _Disjunction<_Next::value, _Next, _Rest...>::type;
+    using type = typename _Disjunction<static_cast<bool>(_Next::value), _Next, _Rest...>::type;
 };
 
 _EXPORT_STD template <class... _Traits>
 struct disjunction : false_type {}; // If _Traits is empty, false_type
 
 template <class _First, class... _Rest>
-struct disjunction<_First, _Rest...> : _Disjunction<_First::value, _First, _Rest...>::type {
+struct disjunction<_First, _Rest...> : _Disjunction<static_cast<bool>(_First::value), _First, _Rest...>::type {
     // the first true trait in _Traits, or the last trait if none are true
 };
 

tests/libcxx/expected_results.txt

@@ -365,6 +365,12 @@ std/algorithms/alg.modifying.operations/alg.move/move.pass.cpp:1 FAIL
 std/language.support/support.rtti/type.info/type_info.equal.pass.cpp:0 FAIL
 std/language.support/support.rtti/type.info/type_info.equal.pass.cpp:1 FAIL
 
+# VSO-2170500 C1XX's type trait optimization mishandles conjunction/disjunction with non-bool types
+std/utilities/meta/meta.logical/conjunction.compile.pass.cpp:0 FAIL
+std/utilities/meta/meta.logical/conjunction.compile.pass.cpp:1 FAIL
+std/utilities/meta/meta.logical/disjunction.compile.pass.cpp:0 FAIL
+std/utilities/meta/meta.logical/disjunction.compile.pass.cpp:1 FAIL
+
 
 # *** CLANG COMPILER BUGS ***
 # LLVM-46207 Clang's tgmath.h interferes with the UCRT's tgmath.h
@@ -891,12 +897,6 @@ std/ranges/range.adaptors/range.lazy.split/range.lazy.split.inner/iter_swap.pass
 # Not analyzed. Checking whether packaged_task is constructible from an allocator and a packaged_task of a different type.
 std/thread/futures/futures.task/futures.task.members/ctor2.compile.pass.cpp FAIL
 
-# Not analyzed.
-# MSVC warning C4305: 'specialization': truncation from 'const int' to 'bool'
-# Clang error: non-type template argument evaluates to -1, which cannot be narrowed to type 'bool' [-Wc++11-narrowing]
-std/utilities/meta/meta.logical/conjunction.compile.pass.cpp FAIL
-std/utilities/meta/meta.logical/disjunction.compile.pass.cpp FAIL
-
 # Not analyzed. Possible MSVC compiler bug, this is inspecting type trait behavior.
 std/utilities/meta/meta.unary/meta.unary.prop/is_nothrow_copy_assignable.pass.cpp:0 FAIL
 std/utilities/meta/meta.unary/meta.unary.prop/is_nothrow_copy_assignable.pass.cpp:1 FAIL

tests/std/test.lst

@@ -248,6 +248,7 @@ tests\GH_004609_heterogeneous_cmp_overloads
 tests\GH_004618_mixed_operator_usage_keeps_statistical_properties
 tests\GH_004618_normal_distribution_avoids_resets
 tests\GH_004657_expected_constraints_permissive
+tests\GH_004845_logical_operator_traits_with_non_bool_constant
 tests\LWG2381_num_get_floating_point
 tests\LWG2597_complex_branch_cut
 tests\LWG3018_shared_ptr_function

tests/std/tests/GH_004845_logical_operator_traits_with_non_bool_constant/env.lst

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

tests/std/tests/GH_004845_logical_operator_traits_with_non_bool_constant/test.compile.pass.cpp

@@ -0,0 +1,59 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// GH-4845 <type_traits>: Logical operator traits with non-bool_constant arguments emit truncation warnings
+
+#include <type_traits>
+using namespace std;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+template <class Base, class Derived>
+void test_base_derived() {
+    STATIC_ASSERT(is_base_of_v<Base, Derived>);
+    using ValueType = typename Base::value_type;
+    STATIC_ASSERT(is_same_v<const ValueType, decltype(Derived::type::value)>);
+    STATIC_ASSERT(Base::value == Derived::type::value);
+#if defined(__clang__) || defined(__EDG__) // TRANSITION, VSO-2170500 (C1XX type trait optimization)
+    STATIC_ASSERT(is_same_v<const ValueType, decltype(Derived::value)>);
+    STATIC_ASSERT(Base::value == Derived::value);
+#endif // ^^^ no workaround ^^^
+}
+
+template <short N>
+using SC = integral_constant<short, N>;
+template <long N>
+using LC = integral_constant<long, N>;
+
+// This test is verifying the absence of truncation warnings, so it uses integral values of 2 or greater for "true"
+// values, skipping 1. It also tests these values in both the "first" and "next" positions, as they were both affected.
+
+void test_conjunction() {
+    // N4986 [meta.logical]/5:
+    // The specialization conjunction<B1, ..., BN> has a public and unambiguous base that is either
+    // - the first type Bi in the list true_type, B1, ..., BN for which bool(Bi::value) is false, or
+    // - if there is no such Bi, the last type in the list.
+    test_base_derived<LC<3>, conjunction<SC<2>, LC<3>>>();
+    test_base_derived<LC<0>, conjunction<SC<4>, LC<0>>>();
+    test_base_derived<SC<0>, conjunction<SC<0>, LC<5>>>();
+    test_base_derived<SC<0>, conjunction<SC<0>, LC<0>>>();
+}
+
+void test_disjunction() {
+    // N4986 [meta.logical]/10:
+    // The specialization disjunction<B1, ..., BN> has a public and unambiguous base that is either
+    // - the first type Bi in the list false_type, B1, ..., BN for which bool(Bi::value) is true, or
+    // - if there is no such Bi, the last type in the list.
+    test_base_derived<SC<6>, disjunction<SC<6>, LC<7>>>();
+    test_base_derived<SC<8>, disjunction<SC<8>, LC<0>>>();
+    test_base_derived<LC<9>, disjunction<SC<0>, LC<9>>>();
+    test_base_derived<LC<0>, disjunction<SC<0>, LC<0>>>();
+}
+
+void test_negation() {
+    // N4986 [meta.logical]/12:
+    // The class template negation forms the logical negation of its template type argument.
+    // The type negation<B> is a Cpp17UnaryTypeTrait with a base characteristic of bool_constant<!bool(B::value)>.
+    test_base_derived<false_type, negation<SC<1729>>>();
+    test_base_derived<true_type, negation<SC<0>>>();
+}