Fixes for C++23

std::result_of is removed.
GetLValue appears to be move-ing x. P2266R3

Fixes: #240
PiperOrigin-RevId: 783643789
Change-Id: I5e6fd58b2c88c85c5b86f0417df8dc2b956dfdae

Author: laramiel

tensorstore/internal/BUILD

@@ -1632,7 +1632,10 @@ tensorstore_cc_test(
 tensorstore_cc_library(
     name = "compare",
     hdrs = ["compare.h"],
-    deps = ["@abseil-cpp//absl/types:compare"],
+    deps = [
+        "@abseil-cpp//absl/meta:type_traits",
+        "@abseil-cpp//absl/types:compare",
+    ],
 )
 
 tensorstore_cc_test(

tensorstore/internal/cache/cache.h

@@ -158,57 +158,6 @@ class CachePool : private internal_cache::CachePoolImpl {
   friend class internal_cache::Access;
 };
 
-/// Returns a cache of type `CacheType` for the specified `cache_key`.
-///
-/// If such a cache does not already exist, or `cache_key` is empty,
-/// `make_cache()` is called to obtain a new such cache.
-///
-/// \tparam CacheType Must be a class that inherits from `Cache`, or defines a
-///     `Cache& cache()` method.
-/// \param pool Cache pool, may be `nullptr` to indicate that caching is
-///     disabled.
-/// \param type_info Additional key used in looking up the cache.  Has no effect
-///     if `cache_key` is the empty string or `pool` is `nullptr`.  Set to
-///     `typeid(CacheType)` when calling `GetCache`, but can be any arbitrary
-///     `std::type_info` object.
-/// \param cache_key Specifies the cache key.
-/// \param make_cache Nullary function that returns an
-///     `std::unique_ptr<CacheType>`, where `CacheType` as a type that inherits
-///     from `Cache` or defines a `Cache& cache()` method.  A `nullptr` may be
-///     returned to indicate an error creating the cache (any additional error
-///     information must be communicated via some separate out-of-band channel).
-template <typename CacheType, typename MakeCache>
-CachePtr<CacheType> GetCacheWithExplicitTypeInfo(
-    CachePool* pool, const std::type_info& type_info,
-    std::string_view cache_key, MakeCache&& make_cache) {
-  auto cache = internal_cache::GetCacheInternal(
-      internal_cache::Access::StaticCast<internal_cache::CachePoolImpl>(pool),
-      type_info, cache_key, [&]() -> std::unique_ptr<internal::Cache> {
-        std::unique_ptr<CacheType> cache = make_cache();
-        if (!cache) return nullptr;
-        void* user_ptr = cache.get();
-        auto base_ptr = std::unique_ptr<internal::Cache>(
-            &internal_cache::GetCacheObject(cache.release()));
-        internal_cache::Access::StaticCast<internal_cache::CacheImpl>(
-            base_ptr.get())
-            ->user_ptr_ = user_ptr;
-        return base_ptr;
-      });
-  if (!cache) return nullptr;
-  return CachePtr<CacheType>(
-      static_cast<CacheType*>(
-          internal_cache::Access::StaticCast<internal_cache::CacheImpl>(
-              cache.release())
-              ->user_ptr_),
-      internal::adopt_object_ref);
-}
-template <typename CacheType, typename MakeCache>
-CachePtr<CacheType> GetCache(CachePool* pool, std::string_view cache_key,
-                             MakeCache&& make_cache) {
-  return GetCacheWithExplicitTypeInfo<CacheType>(
-      pool, typeid(CacheType), cache_key, std::forward<MakeCache>(make_cache));
-}
-
 /// Pointer to a cache entry that prevents it from being evicted due to memory
 /// pressure, but still permits it to be destroyed if its parent cache is
 /// destroyed.
@@ -373,6 +322,57 @@ class Cache : private internal_cache::CacheImpl {
   friend class internal_cache::Access;
 };
 
+/// Returns a cache of type `CacheType` for the specified `cache_key`.
+///
+/// If such a cache does not already exist, or `cache_key` is empty,
+/// `make_cache()` is called to obtain a new such cache.
+///
+/// \tparam CacheType Must be a class that inherits from `Cache`, or defines a
+///     `Cache& cache()` method.
+/// \param pool Cache pool, may be `nullptr` to indicate that caching is
+///     disabled.
+/// \param type_info Additional key used in looking up the cache.  Has no effect
+///     if `cache_key` is the empty string or `pool` is `nullptr`.  Set to
+///     `typeid(CacheType)` when calling `GetCache`, but can be any arbitrary
+///     `std::type_info` object.
+/// \param cache_key Specifies the cache key.
+/// \param make_cache Nullary function that returns an
+///     `std::unique_ptr<CacheType>`, where `CacheType` as a type that inherits
+///     from `Cache` or defines a `Cache& cache()` method.  A `nullptr` may be
+///     returned to indicate an error creating the cache (any additional error
+///     information must be communicated via some separate out-of-band channel).
+template <typename CacheType, typename MakeCache>
+CachePtr<CacheType> GetCacheWithExplicitTypeInfo(
+    CachePool* pool, const std::type_info& type_info,
+    std::string_view cache_key, MakeCache&& make_cache) {
+  auto cache = internal_cache::GetCacheInternal(
+      internal_cache::Access::StaticCast<internal_cache::CachePoolImpl>(pool),
+      type_info, cache_key, [&]() -> std::unique_ptr<internal::Cache> {
+        std::unique_ptr<CacheType> cache = make_cache();
+        if (!cache) return nullptr;
+        void* user_ptr = cache.get();
+        auto base_ptr = std::unique_ptr<internal::Cache>(
+            &internal_cache::GetCacheObject(cache.release()));
+        internal_cache::Access::StaticCast<internal_cache::CacheImpl>(
+            base_ptr.get())
+            ->user_ptr_ = user_ptr;
+        return base_ptr;
+      });
+  if (!cache) return nullptr;
+  return CachePtr<CacheType>(
+      static_cast<CacheType*>(
+          internal_cache::Access::StaticCast<internal_cache::CacheImpl>(
+              cache.release())
+              ->user_ptr_),
+      internal::adopt_object_ref);
+}
+template <typename CacheType, typename MakeCache>
+CachePtr<CacheType> GetCache(CachePool* pool, std::string_view cache_key,
+                             MakeCache&& make_cache) {
+  return GetCacheWithExplicitTypeInfo<CacheType>(
+      pool, typeid(CacheType), cache_key, std::forward<MakeCache>(make_cache));
+}
+
 /// Returns a reference to the cache that contains `entry`.  The reference
 /// lifetime is tied to the lifetime of `entry`, but the lifetime of the cache
 /// may be extended by creating a CachePtr.

tensorstore/internal/compare.h

@@ -17,6 +17,7 @@
 
 #include <type_traits>
 
+#include "absl/meta/type_traits.h"
 #include "absl/types/compare.h"
 
 namespace tensorstore {
@@ -42,7 +43,7 @@ constexpr inline absl::weak_ordering CompareResultAsWeakOrdering(
 // integer value, as in `std::string_view::compare`.
 template <
     typename Compare, typename K, typename LK,
-    std::enable_if_t<!std::is_same<bool, std::result_of_t<Compare(
+    std::enable_if_t<!std::is_same<bool, absl::result_of_t<Compare(
                                              const K &, const LK &)>>::value,
                      int> = 0>
 constexpr absl::weak_ordering DoThreeWayComparison(const Compare &compare,
@@ -52,7 +53,7 @@ constexpr absl::weak_ordering DoThreeWayComparison(const Compare &compare,
 
 template <
     typename Compare, typename K, typename LK,
-    std::enable_if_t<std::is_same<bool, std::result_of_t<Compare(
+    std::enable_if_t<std::is_same<bool, absl::result_of_t<Compare(
                                             const K &, const LK &)>>::value,
                      int> = 0>
 constexpr absl::weak_ordering DoThreeWayComparison(const Compare &compare,

tensorstore/internal/meta/type_traits.h

@@ -203,7 +203,7 @@ using CopyQualifiers =
 /// for specifying default argument values.
 template <typename T>
 inline T& GetLValue(T&& x) {
-  return x;
+  return static_cast<T&>(x);
 }
 
 /// Type alias that evaluates to its first argument.  Additional type arguments,