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// Copyright 2023 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef ABSL_BASE_INTERNAL_NULLABILITY_IMPL_H_
#define ABSL_BASE_INTERNAL_NULLABILITY_IMPL_H_
#include <memory>
#include <type_traits>
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/meta/type_traits.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace nullability_internal {
// `IsNullabilityCompatible` checks whether its first argument is a class
// explicitly tagged as supporting nullability annotations. The tag is the type
// declaration `absl_nullability_compatible`.
template <typename, typename = void>
struct IsNullabilityCompatible : std::false_type {};
template <typename T>
struct IsNullabilityCompatible<
T, absl::void_t<typename T::absl_nullability_compatible>> : std::true_type {
};
template <typename T>
constexpr bool IsSupportedType = IsNullabilityCompatible<T>::value;
template <typename T>
constexpr bool IsSupportedType<T*> = true;
template <typename T, typename U>
constexpr bool IsSupportedType<T U::*> = true;
template <typename T, typename... Deleter>
constexpr bool IsSupportedType<std::unique_ptr<T, Deleter...>> = true;
template <typename T>
constexpr bool IsSupportedType<std::shared_ptr<T>> = true;
template <typename T>
struct EnableNullable {
static_assert(nullability_internal::IsSupportedType<std::remove_cv_t<T>>,
"Template argument must be a raw or supported smart pointer "
"type. See absl/base/nullability.h.");
using type = T;
};
template <typename T>
struct EnableNonnull {
static_assert(nullability_internal::IsSupportedType<std::remove_cv_t<T>>,
"Template argument must be a raw or supported smart pointer "
"type. See absl/base/nullability.h.");
using type = T;
};
template <typename T>
struct EnableNullabilityUnknown {
static_assert(nullability_internal::IsSupportedType<std::remove_cv_t<T>>,
"Template argument must be a raw or supported smart pointer "
"type. See absl/base/nullability.h.");
using type = T;
};
// Note: we do not apply Clang nullability attributes (e.g. _Nullable). These
// only support raw pointers, and conditionally enabling them only for raw
// pointers inhibits template arg deduction. Ideally, they would support all
// pointer-like types.
template <typename T, typename = typename EnableNullable<T>::type>
using NullableImpl
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::annotate)
[[clang::annotate("Nullable")]]
#endif
= T;
template <typename T, typename = typename EnableNonnull<T>::type>
using NonnullImpl
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::annotate)
[[clang::annotate("Nonnull")]]
#endif
= T;
template <typename T, typename = typename EnableNullabilityUnknown<T>::type>
using NullabilityUnknownImpl
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::annotate)
[[clang::annotate("Nullability_Unspecified")]]
#endif
= T;
} // namespace nullability_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_BASE_INTERNAL_NULLABILITY_IMPL_H_
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