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+// Copyright 2018 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.
+
+#include "absl/functional/bind_front.h"
+
+#include <stddef.h>
+
+#include <functional>
+#include <memory>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/memory/memory.h"
+
+namespace {
+
+char CharAt(const char* s, size_t index) { return s[index]; }
+
+TEST(BindTest, Basics) {
+ EXPECT_EQ('C', absl::bind_front(CharAt)("ABC", 2));
+ EXPECT_EQ('C', absl::bind_front(CharAt, "ABC")(2));
+ EXPECT_EQ('C', absl::bind_front(CharAt, "ABC", 2)());
+}
+
+TEST(BindTest, Lambda) {
+ auto lambda = [](int x, int y, int z) { return x + y + z; };
+ EXPECT_EQ(6, absl::bind_front(lambda)(1, 2, 3));
+ EXPECT_EQ(6, absl::bind_front(lambda, 1)(2, 3));
+ EXPECT_EQ(6, absl::bind_front(lambda, 1, 2)(3));
+ EXPECT_EQ(6, absl::bind_front(lambda, 1, 2, 3)());
+}
+
+struct Functor {
+ std::string operator()() & { return "&"; }
+ std::string operator()() const& { return "const&"; }
+ std::string operator()() && { return "&&"; }
+ std::string operator()() const&& { return "const&&"; }
+};
+
+TEST(BindTest, PerfectForwardingOfBoundArgs) {
+ auto f = absl::bind_front(Functor());
+ const auto& cf = f;
+ EXPECT_EQ("&", f());
+ EXPECT_EQ("const&", cf());
+ EXPECT_EQ("&&", std::move(f)());
+ EXPECT_EQ("const&&", std::move(cf)());
+}
+
+struct ArgDescribe {
+ std::string operator()(int&) const { return "&"; } // NOLINT
+ std::string operator()(const int&) const { return "const&"; } // NOLINT
+ std::string operator()(int&&) const { return "&&"; }
+ std::string operator()(const int&&) const { return "const&&"; }
+};
+
+TEST(BindTest, PerfectForwardingOfFreeArgs) {
+ ArgDescribe f;
+ int i;
+ EXPECT_EQ("&", absl::bind_front(f)(static_cast<int&>(i)));
+ EXPECT_EQ("const&", absl::bind_front(f)(static_cast<const int&>(i)));
+ EXPECT_EQ("&&", absl::bind_front(f)(static_cast<int&&>(i)));
+ EXPECT_EQ("const&&", absl::bind_front(f)(static_cast<const int&&>(i)));
+}
+
+struct NonCopyableFunctor {
+ NonCopyableFunctor() = default;
+ NonCopyableFunctor(const NonCopyableFunctor&) = delete;
+ NonCopyableFunctor& operator=(const NonCopyableFunctor&) = delete;
+ const NonCopyableFunctor* operator()() const { return this; }
+};
+
+TEST(BindTest, RefToFunctor) {
+ // It won't copy/move the functor and use the original object.
+ NonCopyableFunctor ncf;
+ auto bound_ncf = absl::bind_front(std::ref(ncf));
+ auto bound_ncf_copy = bound_ncf;
+ EXPECT_EQ(&ncf, bound_ncf_copy());
+}
+
+struct Struct {
+ std::string value;
+};
+
+TEST(BindTest, StoreByCopy) {
+ Struct s = {"hello"};
+ auto f = absl::bind_front(&Struct::value, s);
+ auto g = f;
+ EXPECT_EQ("hello", f());
+ EXPECT_EQ("hello", g());
+ EXPECT_NE(&s.value, &f());
+ EXPECT_NE(&s.value, &g());
+ EXPECT_NE(&g(), &f());
+}
+
+struct NonCopyable {
+ explicit NonCopyable(const std::string& s) : value(s) {}
+ NonCopyable(const NonCopyable&) = delete;
+ NonCopyable& operator=(const NonCopyable&) = delete;
+
+ std::string value;
+};
+
+const std::string& GetNonCopyableValue(const NonCopyable& n) { return n.value; }
+
+TEST(BindTest, StoreByRef) {
+ NonCopyable s("hello");
+ auto f = absl::bind_front(&GetNonCopyableValue, std::ref(s));
+ EXPECT_EQ("hello", f());
+ EXPECT_EQ(&s.value, &f());
+ auto g = std::move(f); // NOLINT
+ EXPECT_EQ("hello", g());
+ EXPECT_EQ(&s.value, &g());
+ s.value = "goodbye";
+ EXPECT_EQ("goodbye", g());
+}
+
+TEST(BindTest, StoreByCRef) {
+ NonCopyable s("hello");
+ auto f = absl::bind_front(&GetNonCopyableValue, std::cref(s));
+ EXPECT_EQ("hello", f());
+ EXPECT_EQ(&s.value, &f());
+ auto g = std::move(f); // NOLINT
+ EXPECT_EQ("hello", g());
+ EXPECT_EQ(&s.value, &g());
+ s.value = "goodbye";
+ EXPECT_EQ("goodbye", g());
+}
+
+const std::string& GetNonCopyableValueByWrapper(
+ std::reference_wrapper<NonCopyable> n) {
+ return n.get().value;
+}
+
+TEST(BindTest, StoreByRefInvokeByWrapper) {
+ NonCopyable s("hello");
+ auto f = absl::bind_front(GetNonCopyableValueByWrapper, std::ref(s));
+ EXPECT_EQ("hello", f());
+ EXPECT_EQ(&s.value, &f());
+ auto g = std::move(f);
+ EXPECT_EQ("hello", g());
+ EXPECT_EQ(&s.value, &g());
+ s.value = "goodbye";
+ EXPECT_EQ("goodbye", g());
+}
+
+TEST(BindTest, StoreByPointer) {
+ NonCopyable s("hello");
+ auto f = absl::bind_front(&NonCopyable::value, &s);
+ EXPECT_EQ("hello", f());
+ EXPECT_EQ(&s.value, &f());
+ auto g = std::move(f);
+ EXPECT_EQ("hello", g());
+ EXPECT_EQ(&s.value, &g());
+}
+
+int Sink(std::unique_ptr<int> p) {
+ return *p;
+}
+
+std::unique_ptr<int> Factory(int n) { return absl::make_unique<int>(n); }
+
+TEST(BindTest, NonCopyableArg) {
+ EXPECT_EQ(42, absl::bind_front(Sink)(absl::make_unique<int>(42)));
+ EXPECT_EQ(42, absl::bind_front(Sink, absl::make_unique<int>(42))());
+}
+
+TEST(BindTest, NonCopyableResult) {
+ EXPECT_THAT(absl::bind_front(Factory)(42), ::testing::Pointee(42));
+ EXPECT_THAT(absl::bind_front(Factory, 42)(), ::testing::Pointee(42));
+}
+
+// is_copy_constructible<FalseCopyable<unique_ptr<T>> is true but an attempt to
+// instantiate the copy constructor leads to a compile error. This is similar
+// to how standard containers behave.
+template <class T>
+struct FalseCopyable {
+ FalseCopyable() {}
+ FalseCopyable(const FalseCopyable& other) : m(other.m) {}
+ FalseCopyable(FalseCopyable&& other) : m(std::move(other.m)) {}
+ T m;
+};
+
+int GetMember(FalseCopyable<std::unique_ptr<int>> x) { return *x.m; }
+
+TEST(BindTest, WrappedMoveOnly) {
+ FalseCopyable<std::unique_ptr<int>> x;
+ x.m = absl::make_unique<int>(42);
+ auto f = absl::bind_front(&GetMember, std::move(x));
+ EXPECT_EQ(42, std::move(f)());
+}
+
+int Plus(int a, int b) { return a + b; }
+
+TEST(BindTest, ConstExpr) {
+ constexpr auto f = absl::bind_front(CharAt);
+ EXPECT_EQ(f("ABC", 1), 'B');
+ static constexpr int five = 5;
+ constexpr auto plus5 = absl::bind_front(Plus, five);
+ EXPECT_EQ(plus5(1), 6);
+
+ // There seems to be a bug in MSVC dealing constexpr construction of
+ // char[]. Notice 'plus5' above; 'int' works just fine.
+#if !(defined(_MSC_VER) && _MSC_VER < 1910)
+ static constexpr char data[] = "DEF";
+ constexpr auto g = absl::bind_front(CharAt, data);
+ EXPECT_EQ(g(1), 'E');
+#endif
+}
+
+struct ManglingCall {
+ int operator()(int, double, std::string) const { return 0; }
+};
+
+TEST(BindTest, Mangling) {
+ // We just want to generate a particular instantiation to see its mangling.
+ absl::bind_front(ManglingCall{}, 1, 3.3)("A");
+}
+
+} // namespace