1 files changed, 176 insertions, 2 deletions
diff --git a/absl/utility/utility_test.cc b/absl/utility/utility_test.cc
index 62cb46f4..342165ed 100644
--- a/absl/utility/utility_test.cc
+++ b/absl/utility/utility_test.cc
@@ -23,6 +23,8 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/attributes.h"
+#include "absl/memory/memory.h"
+#include "absl/strings/str_cat.h"
 
 namespace {
 
@@ -38,8 +40,9 @@ namespace {
 #pragma warning( disable : 4101 )  // unreferenced local variable
 #endif  // _MSC_VER
 
-using testing::StaticAssertTypeEq;
-using testing::ElementsAre;
+using ::testing::ElementsAre;
+using ::testing::Pointee;
+using ::testing::StaticAssertTypeEq;
 
 TEST(IntegerSequenceTest, ValueType) {
   StaticAssertTypeEq<int, absl::integer_sequence<int>::value_type>();
@@ -159,5 +162,176 @@ TEST(IndexSequenceForTest, Example) {
               ElementsAre("12", "abc", "3.14"));
 }
 
+int Function(int a, int b) { return a - b; }
+
+int Sink(std::unique_ptr<int> p) { return *p; }
+
+std::unique_ptr<int> Factory(int n) { return absl::make_unique<int>(n); }
+
+void NoOp() {}
+
+struct ConstFunctor {
+  int operator()(int a, int b) const { return a - b; }
+};
+
+struct MutableFunctor {
+  int operator()(int a, int b) { return a - b; }
+};
+
+struct EphemeralFunctor {
+  EphemeralFunctor() {}
+  EphemeralFunctor(const EphemeralFunctor&) {}
+  EphemeralFunctor(EphemeralFunctor&&) {}
+  int operator()(int a, int b) && { return a - b; }
+};
+
+struct OverloadedFunctor {
+  OverloadedFunctor() {}
+  OverloadedFunctor(const OverloadedFunctor&) {}
+  OverloadedFunctor(OverloadedFunctor&&) {}
+  template <typename... Args>
+  std::string operator()(const Args&... args) & {
+    return absl::StrCat("&", args...);
+  }
+  template <typename... Args>
+  std::string operator()(const Args&... args) const& {
+    return absl::StrCat("const&", args...);
+  }
+  template <typename... Args>
+  std::string operator()(const Args&... args) && {
+    return absl::StrCat("&&", args...);
+  }
+};
+
+struct Class {
+  int Method(int a, int b) { return a - b; }
+  int ConstMethod(int a, int b) const { return a - b; }
+
+  int member;
+};
+
+struct FlipFlop {
+  int ConstMethod() const { return member; }
+  FlipFlop operator*() const { return {-member}; }
+
+  int member;
+};
+
+TEST(ApplyTest, Function) {
+  EXPECT_EQ(1, absl::apply(Function, std::make_tuple(3, 2)));
+  EXPECT_EQ(1, absl::apply(&Function, std::make_tuple(3, 2)));
+}
+
+TEST(ApplyTest, NonCopyableArgument) {
+  EXPECT_EQ(42, absl::apply(Sink, std::make_tuple(absl::make_unique<int>(42))));
+}
+
+TEST(ApplyTest, NonCopyableResult) {
+  EXPECT_THAT(absl::apply(Factory, std::make_tuple(42)),
+              ::testing::Pointee(42));
+}
+
+TEST(ApplyTest, VoidResult) { absl::apply(NoOp, std::tuple<>()); }
+
+TEST(ApplyTest, ConstFunctor) {
+  EXPECT_EQ(1, absl::apply(ConstFunctor(), std::make_tuple(3, 2)));
+}
+
+TEST(ApplyTest, MutableFunctor) {
+  MutableFunctor f;
+  EXPECT_EQ(1, absl::apply(f, std::make_tuple(3, 2)));
+  EXPECT_EQ(1, absl::apply(MutableFunctor(), std::make_tuple(3, 2)));
+}
+TEST(ApplyTest, EphemeralFunctor) {
+  EphemeralFunctor f;
+  EXPECT_EQ(1, absl::apply(std::move(f), std::make_tuple(3, 2)));
+  EXPECT_EQ(1, absl::apply(EphemeralFunctor(), std::make_tuple(3, 2)));
+}
+TEST(ApplyTest, OverloadedFunctor) {
+  OverloadedFunctor f;
+  const OverloadedFunctor& cf = f;
+
+  EXPECT_EQ("&", absl::apply(f, std::tuple<>{}));
+  EXPECT_EQ("& 42", absl::apply(f, std::make_tuple(" 42")));
+
+  EXPECT_EQ("const&", absl::apply(cf, std::tuple<>{}));
+  EXPECT_EQ("const& 42", absl::apply(cf, std::make_tuple(" 42")));
+
+  EXPECT_EQ("&&", absl::apply(std::move(f), std::tuple<>{}));
+  OverloadedFunctor f2;
+  EXPECT_EQ("&& 42", absl::apply(std::move(f2), std::make_tuple(" 42")));
+}
+
+TEST(ApplyTest, ReferenceWrapper) {
+  ConstFunctor cf;
+  MutableFunctor mf;
+  EXPECT_EQ(1, absl::apply(std::cref(cf), std::make_tuple(3, 2)));
+  EXPECT_EQ(1, absl::apply(std::ref(cf), std::make_tuple(3, 2)));
+  EXPECT_EQ(1, absl::apply(std::ref(mf), std::make_tuple(3, 2)));
+}
+
+TEST(ApplyTest, MemberFunction) {
+  std::unique_ptr<Class> p(new Class);
+  std::unique_ptr<const Class> cp(new Class);
+  EXPECT_EQ(
+      1, absl::apply(&Class::Method,
+                     std::tuple<std::unique_ptr<Class>&, int, int>(p, 3, 2)));
+  EXPECT_EQ(1, absl::apply(&Class::Method,
+                           std::tuple<Class*, int, int>(p.get(), 3, 2)));
+  EXPECT_EQ(
+      1, absl::apply(&Class::Method, std::tuple<Class&, int, int>(*p, 3, 2)));
+
+  EXPECT_EQ(
+      1, absl::apply(&Class::ConstMethod,
+                     std::tuple<std::unique_ptr<Class>&, int, int>(p, 3, 2)));
+  EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
+                           std::tuple<Class*, int, int>(p.get(), 3, 2)));
+  EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
+                           std::tuple<Class&, int, int>(*p, 3, 2)));
+
+  EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
+                           std::tuple<std::unique_ptr<const Class>&, int, int>(
+                               cp, 3, 2)));
+  EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
+                           std::tuple<const Class*, int, int>(cp.get(), 3, 2)));
+  EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
+                           std::tuple<const Class&, int, int>(*cp, 3, 2)));
+
+  EXPECT_EQ(1, absl::apply(&Class::Method,
+                           std::make_tuple(absl::make_unique<Class>(), 3, 2)));
+  EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
+                           std::make_tuple(absl::make_unique<Class>(), 3, 2)));
+  EXPECT_EQ(
+      1, absl::apply(&Class::ConstMethod,
+                     std::make_tuple(absl::make_unique<const Class>(), 3, 2)));
+}
+
+TEST(ApplyTest, DataMember) {
+  std::unique_ptr<Class> p(new Class{42});
+  std::unique_ptr<const Class> cp(new Class{42});
+  EXPECT_EQ(
+      42, absl::apply(&Class::member, std::tuple<std::unique_ptr<Class>&>(p)));
+  EXPECT_EQ(42, absl::apply(&Class::member, std::tuple<Class&>(*p)));
+  EXPECT_EQ(42, absl::apply(&Class::member, std::tuple<Class*>(p.get())));
+
+  absl::apply(&Class::member, std::tuple<std::unique_ptr<Class>&>(p)) = 42;
+  absl::apply(&Class::member, std::tuple<Class*>(p.get())) = 42;
+  absl::apply(&Class::member, std::tuple<Class&>(*p)) = 42;
+
+  EXPECT_EQ(42, absl::apply(&Class::member,
+                            std::tuple<std::unique_ptr<const Class>&>(cp)));
+  EXPECT_EQ(42, absl::apply(&Class::member, std::tuple<const Class&>(*cp)));
+  EXPECT_EQ(42,
+            absl::apply(&Class::member, std::tuple<const Class*>(cp.get())));
+}
+
+TEST(ApplyTest, FlipFlop) {
+  FlipFlop obj = {42};
+  // This call could resolve to (obj.*&FlipFlop::ConstMethod)() or
+  // ((*obj).*&FlipFlop::ConstMethod)(). We verify that it's the former.
+  EXPECT_EQ(42, absl::apply(&FlipFlop::ConstMethod, std::make_tuple(obj)));
+  EXPECT_EQ(42, absl::apply(&FlipFlop::member, std::make_tuple(obj)));
+}
+
 }  // namespace