folly/test/OptionalTest.cpp

   1 /*
   2  * Copyright 2017 Facebook, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *   http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <folly/Optional.h>
  18 #include <folly/Portability.h>
  19 #include <folly/portability/GTest.h>
  20
  21 #include <algorithm>
  22 #include <iomanip>
  23 #include <memory>
  24 #include <string>
  25 #include <type_traits>
  26 #include <unordered_map>
  27 #include <vector>
  28
  29 #include <boost/optional.hpp>
  30
  31 using std::unique_ptr;
  32 using std::shared_ptr;
  33
  34 namespace folly {
  35
  36 template <class V>
  37 std::ostream& operator<<(std::ostream& os, const Optional<V>& v) {
  38   if (v) {
  39     os << "Optional(" << v.value() << ')';
  40   } else {
  41     os << "None";
  42   }
  43   return os;
  44 }
  45
  46 struct NoDefault {
  47   NoDefault(int, int) {}
  48   char a, b, c;
  49 };
  50
  51 static_assert(sizeof(Optional<char>) == 2, "");
  52 static_assert(sizeof(Optional<int>) == 8, "");
  53 static_assert(sizeof(Optional<NoDefault>) == 4, "");
  54 static_assert(sizeof(Optional<char>) == sizeof(boost::optional<char>), "");
  55 static_assert(sizeof(Optional<short>) == sizeof(boost::optional<short>), "");
  56 static_assert(sizeof(Optional<int>) == sizeof(boost::optional<int>), "");
  57 static_assert(sizeof(Optional<double>) == sizeof(boost::optional<double>), "");
  58
  59 TEST(Optional, NoDefault) {
  60   Optional<NoDefault> x;
  61   EXPECT_FALSE(x);
  62   x.emplace(4, 5);
  63   EXPECT_TRUE(bool(x));
  64   x.clear();
  65   EXPECT_FALSE(x);
  66 }
  67
  68 TEST(Optional, String) {
  69   Optional<std::string> maybeString;
  70   EXPECT_FALSE(maybeString);
  71   maybeString = "hello";
  72   EXPECT_TRUE(bool(maybeString));
  73 }
  74
  75 TEST(Optional, Const) {
  76   { // default construct
  77     Optional<const int> opt;
  78     EXPECT_FALSE(bool(opt));
  79     opt.emplace(4);
  80     EXPECT_EQ(*opt, 4);
  81     opt.emplace(5);
  82     EXPECT_EQ(*opt, 5);
  83     opt.clear();
  84     EXPECT_FALSE(bool(opt));
  85   }
  86   { // copy-constructed
  87     const int x = 6;
  88     Optional<const int> opt(x);
  89     EXPECT_EQ(*opt, 6);
  90   }
  91   { // move-constructed
  92     const int x = 7;
  93     Optional<const int> opt(std::move(x));
  94     EXPECT_EQ(*opt, 7);
  95   }
  96   // no assignment allowed
  97 }
  98
  99 TEST(Optional, Simple) {
 100   Optional<int> opt;
 101   EXPECT_FALSE(bool(opt));
 102   EXPECT_EQ(42, opt.value_or(42));
 103   opt = 4;
 104   EXPECT_TRUE(bool(opt));
 105   EXPECT_EQ(4, *opt);
 106   EXPECT_EQ(4, opt.value_or(42));
 107   opt = 5;
 108   EXPECT_EQ(5, *opt);
 109   opt.clear();
 110   EXPECT_FALSE(bool(opt));
 111 }
 112
 113 class MoveTester {
 114  public:
 115   /* implicit */ MoveTester(const char* s) : s_(s) {}
 116   MoveTester(const MoveTester&) = default;
 117   MoveTester(MoveTester&& other) noexcept {
 118     s_ = std::move(other.s_);
 119     other.s_ = "";
 120   }
 121   MoveTester& operator=(const MoveTester&) = default;
 122   MoveTester& operator=(MoveTester&& other) noexcept {
 123     s_ = std::move(other.s_);
 124     other.s_ = "";
 125     return *this;
 126   }
 127
 128  private:
 129   friend bool operator==(const MoveTester& o1, const MoveTester& o2);
 130   std::string s_;
 131 };
 132
 133 bool operator==(const MoveTester& o1, const MoveTester& o2) {
 134   return o1.s_ == o2.s_;
 135 }
 136
 137 TEST(Optional, value_or_rvalue_arg) {
 138   Optional<MoveTester> opt;
 139   MoveTester dflt = "hello";
 140   EXPECT_EQ("hello", opt.value_or(dflt));
 141   EXPECT_EQ("hello", dflt);
 142   EXPECT_EQ("hello", opt.value_or(std::move(dflt)));
 143   EXPECT_EQ("", dflt);
 144   EXPECT_EQ("world", opt.value_or("world"));
 145
 146   dflt = "hello";
 147   // Make sure that the const overload works on const objects
 148   const auto& optc = opt;
 149   EXPECT_EQ("hello", optc.value_or(dflt));
 150   EXPECT_EQ("hello", dflt);
 151   EXPECT_EQ("hello", optc.value_or(std::move(dflt)));
 152   EXPECT_EQ("", dflt);
 153   EXPECT_EQ("world", optc.value_or("world"));
 154
 155   dflt = "hello";
 156   opt = "meow";
 157   EXPECT_EQ("meow", opt.value_or(dflt));
 158   EXPECT_EQ("hello", dflt);
 159   EXPECT_EQ("meow", opt.value_or(std::move(dflt)));
 160   EXPECT_EQ("hello", dflt);  // only moved if used
 161 }
 162
 163 TEST(Optional, value_or_noncopyable) {
 164   Optional<std::unique_ptr<int>> opt;
 165   std::unique_ptr<int> dflt(new int(42));
 166   EXPECT_EQ(42, *std::move(opt).value_or(std::move(dflt)));
 167 }
 168
 169 struct ExpectingDeleter {
 170   explicit ExpectingDeleter(int expected) : expected(expected) { }
 171   int expected;
 172   void operator()(const int* ptr) {
 173     EXPECT_EQ(*ptr, expected);
 174     delete ptr;
 175   }
 176 };
 177
 178 TEST(Optional, value_move) {
 179   auto ptr = Optional<std::unique_ptr<int, ExpectingDeleter>>(
 180       {new int(42), ExpectingDeleter{1337}}).value();
 181   *ptr = 1337;
 182 }
 183
 184 TEST(Optional, dereference_move) {
 185   auto ptr = *Optional<std::unique_ptr<int, ExpectingDeleter>>(
 186       {new int(42), ExpectingDeleter{1337}});
 187   *ptr = 1337;
 188 }
 189
 190 TEST(Optional, EmptyConstruct) {
 191   Optional<int> opt;
 192   EXPECT_FALSE(bool(opt));
 193   Optional<int> test1(opt);
 194   EXPECT_FALSE(bool(test1));
 195   Optional<int> test2(std::move(opt));
 196   EXPECT_FALSE(bool(test2));
 197 }
 198
 199 TEST(Optional, InPlaceConstruct) {
 200   using A = std::pair<int, double>;
 201   Optional<A> opt(in_place, 5, 3.2);
 202   EXPECT_TRUE(bool(opt));
 203   EXPECT_EQ(5, opt->first);
 204 }
 205
 206 TEST(Optional, InPlaceNestedConstruct) {
 207   using A = std::pair<int, double>;
 208   Optional<Optional<A>> opt(in_place, in_place, 5, 3.2);
 209   EXPECT_TRUE(bool(opt));
 210   EXPECT_TRUE(bool(*opt));
 211   EXPECT_EQ(5, (*opt)->first);
 212 }
 213
 214 TEST(Optional, Unique) {
 215   Optional<unique_ptr<int>> opt;
 216
 217   opt.clear();
 218   EXPECT_FALSE(bool(opt));
 219   // empty->emplaced
 220   opt.emplace(new int(5));
 221   EXPECT_TRUE(bool(opt));
 222   EXPECT_EQ(5, **opt);
 223
 224   opt.clear();
 225   // empty->moved
 226   opt = std::make_unique<int>(6);
 227   EXPECT_EQ(6, **opt);
 228   // full->moved
 229   opt = std::make_unique<int>(7);
 230   EXPECT_EQ(7, **opt);
 231
 232   // move it out by move construct
 233   Optional<unique_ptr<int>> moved(std::move(opt));
 234   EXPECT_TRUE(bool(moved));
 235   EXPECT_FALSE(bool(opt));
 236   EXPECT_EQ(7, **moved);
 237
 238   EXPECT_TRUE(bool(moved));
 239   opt = std::move(moved); // move it back by move assign
 240   EXPECT_FALSE(bool(moved));
 241   EXPECT_TRUE(bool(opt));
 242   EXPECT_EQ(7, **opt);
 243 }
 244
 245 TEST(Optional, Shared) {
 246   shared_ptr<int> ptr;
 247   Optional<shared_ptr<int>> opt;
 248   EXPECT_FALSE(bool(opt));
 249   // empty->emplaced
 250   opt.emplace(new int(5));
 251   EXPECT_TRUE(bool(opt));
 252   ptr = opt.value();
 253   EXPECT_EQ(ptr.get(), opt->get());
 254   EXPECT_EQ(2, ptr.use_count());
 255   opt.clear();
 256   EXPECT_EQ(1, ptr.use_count());
 257   // full->copied
 258   opt = ptr;
 259   EXPECT_EQ(2, ptr.use_count());
 260   EXPECT_EQ(ptr.get(), opt->get());
 261   opt.clear();
 262   EXPECT_EQ(1, ptr.use_count());
 263   // full->moved
 264   opt = std::move(ptr);
 265   EXPECT_EQ(1, opt->use_count());
 266   EXPECT_EQ(nullptr, ptr.get());
 267   {
 268     Optional<shared_ptr<int>> copied(opt);
 269     EXPECT_EQ(2, opt->use_count());
 270     Optional<shared_ptr<int>> moved(std::move(opt));
 271     EXPECT_EQ(2, moved->use_count());
 272     moved.emplace(new int(6));
 273     EXPECT_EQ(1, moved->use_count());
 274     copied = moved;
 275     EXPECT_EQ(2, moved->use_count());
 276   }
 277 }
 278
 279 TEST(Optional, Order) {
 280   std::vector<Optional<int>> vect{
 281     { none },
 282     { 3 },
 283     { 1 },
 284     { none },
 285     { 2 },
 286   };
 287   std::vector<Optional<int>> expected {
 288     { none },
 289     { none },
 290     { 1 },
 291     { 2 },
 292     { 3 },
 293   };
 294   std::sort(vect.begin(), vect.end());
 295   EXPECT_EQ(vect, expected);
 296 }
 297
 298 TEST(Optional, Swap) {
 299   Optional<std::string> a;
 300   Optional<std::string> b;
 301
 302   swap(a, b);
 303   EXPECT_FALSE(a.hasValue());
 304   EXPECT_FALSE(b.hasValue());
 305
 306   a = "hello";
 307   EXPECT_TRUE(a.hasValue());
 308   EXPECT_FALSE(b.hasValue());
 309   EXPECT_EQ("hello", a.value());
 310
 311   swap(a, b);
 312   EXPECT_FALSE(a.hasValue());
 313   EXPECT_TRUE(b.hasValue());
 314   EXPECT_EQ("hello", b.value());
 315
 316   a = "bye";
 317   EXPECT_TRUE(a.hasValue());
 318   EXPECT_EQ("bye", a.value());
 319
 320   swap(a, b);
 321 }
 322
 323 TEST(Optional, Comparisons) {
 324   Optional<int> o_;
 325   Optional<int> o1(1);
 326   Optional<int> o2(2);
 327
 328   EXPECT_TRUE(o_ <= (o_));
 329   EXPECT_TRUE(o_ == (o_));
 330   EXPECT_TRUE(o_ >= (o_));
 331
 332   EXPECT_TRUE(o1 < o2);
 333   EXPECT_TRUE(o1 <= o2);
 334   EXPECT_TRUE(o1 <= (o1));
 335   EXPECT_TRUE(o1 == (o1));
 336   EXPECT_TRUE(o1 != o2);
 337   EXPECT_TRUE(o1 >= (o1));
 338   EXPECT_TRUE(o2 >= o1);
 339   EXPECT_TRUE(o2 > o1);
 340
 341   EXPECT_FALSE(o2 < o1);
 342   EXPECT_FALSE(o2 <= o1);
 343   EXPECT_FALSE(o2 <= o1);
 344   EXPECT_FALSE(o2 == o1);
 345   EXPECT_FALSE(o1 != (o1));
 346   EXPECT_FALSE(o1 >= o2);
 347   EXPECT_FALSE(o1 >= o2);
 348   EXPECT_FALSE(o1 > o2);
 349
 350   /* folly::Optional explicitly doesn't support comparisons with contained value
 351   EXPECT_TRUE(1 < o2);
 352   EXPECT_TRUE(1 <= o2);
 353   EXPECT_TRUE(1 <= o1);
 354   EXPECT_TRUE(1 == o1);
 355   EXPECT_TRUE(2 != o1);
 356   EXPECT_TRUE(1 >= o1);
 357   EXPECT_TRUE(2 >= o1);
 358   EXPECT_TRUE(2 > o1);
 359
 360   EXPECT_FALSE(o2 < 1);
 361   EXPECT_FALSE(o2 <= 1);
 362   EXPECT_FALSE(o2 <= 1);
 363   EXPECT_FALSE(o2 == 1);
 364   EXPECT_FALSE(o2 != 2);
 365   EXPECT_FALSE(o1 >= 2);
 366   EXPECT_FALSE(o1 >= 2);
 367   EXPECT_FALSE(o1 > 2);
 368   */
 369
 370   // boost::optional does support comparison with contained value, which can
 371   // lead to confusion when a bool is contained
 372   boost::optional<int> boi(3);
 373   EXPECT_TRUE(boi < 5);
 374   EXPECT_TRUE(boi <= 4);
 375   EXPECT_TRUE(boi == 3);
 376   EXPECT_TRUE(boi != 2);
 377   EXPECT_TRUE(boi >= 1);
 378   EXPECT_TRUE(boi > 0);
 379   EXPECT_TRUE(1 <  boi);
 380   EXPECT_TRUE(2 <= boi);
 381   EXPECT_TRUE(3 == boi);
 382   EXPECT_TRUE(4 != boi);
 383   EXPECT_TRUE(5 >= boi);
 384   EXPECT_TRUE(6 >  boi);
 385
 386   boost::optional<bool> bob(false);
 387   EXPECT_TRUE((bool)bob);
 388   EXPECT_TRUE(bob == false); // well that was confusing
 389   EXPECT_FALSE(bob != false);
 390 }
 391
 392 TEST(Optional, HeterogeneousComparisons) {
 393   using opt8 = Optional<uint8_t>;
 394   using opt64 = Optional<uint64_t>;
 395
 396   EXPECT_TRUE(opt8(4) == uint64_t(4));
 397   EXPECT_FALSE(opt8(8) == uint64_t(4));
 398   EXPECT_FALSE(opt8() == uint64_t(4));
 399
 400   EXPECT_TRUE(uint64_t(4) == opt8(4));
 401   EXPECT_FALSE(uint64_t(4) == opt8(8));
 402   EXPECT_FALSE(uint64_t(4) == opt8());
 403
 404   EXPECT_FALSE(opt8(4) != uint64_t(4));
 405   EXPECT_TRUE(opt8(8) != uint64_t(4));
 406   EXPECT_TRUE(opt8() != uint64_t(4));
 407
 408   EXPECT_FALSE(uint64_t(4) != opt8(4));
 409   EXPECT_TRUE(uint64_t(4) != opt8(8));
 410   EXPECT_TRUE(uint64_t(4) != opt8());
 411
 412   EXPECT_TRUE(opt8() == opt64());
 413   EXPECT_TRUE(opt8(4) == opt64(4));
 414   EXPECT_FALSE(opt8(8) == opt64(4));
 415   EXPECT_FALSE(opt8() == opt64(4));
 416   EXPECT_FALSE(opt8(4) == opt64());
 417
 418   EXPECT_FALSE(opt8() != opt64());
 419   EXPECT_FALSE(opt8(4) != opt64(4));
 420   EXPECT_TRUE(opt8(8) != opt64(4));
 421   EXPECT_TRUE(opt8() != opt64(4));
 422   EXPECT_TRUE(opt8(4) != opt64());
 423
 424   EXPECT_TRUE(opt8() < opt64(4));
 425   EXPECT_TRUE(opt8(4) < opt64(8));
 426   EXPECT_FALSE(opt8() < opt64());
 427   EXPECT_FALSE(opt8(4) < opt64(4));
 428   EXPECT_FALSE(opt8(8) < opt64(4));
 429   EXPECT_FALSE(opt8(4) < opt64());
 430
 431   EXPECT_FALSE(opt8() > opt64(4));
 432   EXPECT_FALSE(opt8(4) > opt64(8));
 433   EXPECT_FALSE(opt8() > opt64());
 434   EXPECT_FALSE(opt8(4) > opt64(4));
 435   EXPECT_TRUE(opt8(8) > opt64(4));
 436   EXPECT_TRUE(opt8(4) > opt64());
 437
 438   EXPECT_TRUE(opt8() <= opt64(4));
 439   EXPECT_TRUE(opt8(4) <= opt64(8));
 440   EXPECT_TRUE(opt8() <= opt64());
 441   EXPECT_TRUE(opt8(4) <= opt64(4));
 442   EXPECT_FALSE(opt8(8) <= opt64(4));
 443   EXPECT_FALSE(opt8(4) <= opt64());
 444
 445   EXPECT_FALSE(opt8() >= opt64(4));
 446   EXPECT_FALSE(opt8(4) >= opt64(8));
 447   EXPECT_TRUE(opt8() >= opt64());
 448   EXPECT_TRUE(opt8(4) >= opt64(4));
 449   EXPECT_TRUE(opt8(8) >= opt64(4));
 450   EXPECT_TRUE(opt8(4) >= opt64());
 451 }
 452
 453 TEST(Optional, NoneComparisons) {
 454   using opt = Optional<int>;
 455   EXPECT_TRUE(opt() == none);
 456   EXPECT_TRUE(none == opt());
 457   EXPECT_FALSE(opt(1) == none);
 458   EXPECT_FALSE(none == opt(1));
 459
 460   EXPECT_FALSE(opt() != none);
 461   EXPECT_FALSE(none != opt());
 462   EXPECT_TRUE(opt(1) != none);
 463   EXPECT_TRUE(none != opt(1));
 464
 465   EXPECT_FALSE(opt() < none);
 466   EXPECT_FALSE(none < opt());
 467   EXPECT_FALSE(opt(1) < none);
 468   EXPECT_TRUE(none < opt(1));
 469
 470   EXPECT_FALSE(opt() > none);
 471   EXPECT_FALSE(none > opt());
 472   EXPECT_FALSE(none > opt(1));
 473   EXPECT_TRUE(opt(1) > none);
 474
 475   EXPECT_TRUE(opt() <= none);
 476   EXPECT_TRUE(none <= opt());
 477   EXPECT_FALSE(opt(1) <= none);
 478   EXPECT_TRUE(none <= opt(1));
 479
 480   EXPECT_TRUE(opt() >= none);
 481   EXPECT_TRUE(none >= opt());
 482   EXPECT_TRUE(opt(1) >= none);
 483   EXPECT_FALSE(none >= opt(1));
 484 }
 485
 486 TEST(Optional, Conversions) {
 487   Optional<bool> mbool;
 488   Optional<short> mshort;
 489   Optional<char*> mstr;
 490   Optional<int> mint;
 491
 492   //These don't compile
 493   //bool b = mbool;
 494   //short s = mshort;
 495   //char* c = mstr;
 496   //int x = mint;
 497   //char* c(mstr);
 498   //short s(mshort);
 499   //int x(mint);
 500
 501   // intended explicit operator bool, for if (opt).
 502   bool b(mbool);
 503   EXPECT_FALSE(b);
 504
 505   // Truthy tests work and are not ambiguous
 506   if (mbool && mshort && mstr && mint) { // only checks not-empty
 507     if (*mbool && *mshort && *mstr && *mint) { // only checks value
 508       ;
 509     }
 510   }
 511
 512   mbool = false;
 513   EXPECT_TRUE(bool(mbool));
 514   EXPECT_FALSE(*mbool);
 515
 516   mbool = true;
 517   EXPECT_TRUE(bool(mbool));
 518   EXPECT_TRUE(*mbool);
 519
 520   mbool = none;
 521   EXPECT_FALSE(bool(mbool));
 522
 523   // No conversion allowed; does not compile
 524   // EXPECT_TRUE(mbool == false);
 525 }
 526
 527 TEST(Optional, Pointee) {
 528   Optional<int> x;
 529   EXPECT_FALSE(get_pointer(x));
 530   x = 1;
 531   EXPECT_TRUE(get_pointer(x));
 532   *get_pointer(x) = 2;
 533   EXPECT_TRUE(*x == 2);
 534   x = none;
 535   EXPECT_FALSE(get_pointer(x));
 536 }
 537
 538 TEST(Optional, MakeOptional) {
 539   // const L-value version
 540   const std::string s("abc");
 541   auto optStr = make_optional(s);
 542   ASSERT_TRUE(optStr.hasValue());
 543   EXPECT_EQ(*optStr, "abc");
 544   *optStr = "cde";
 545   EXPECT_EQ(s, "abc");
 546   EXPECT_EQ(*optStr, "cde");
 547
 548   // L-value version
 549   std::string s2("abc");
 550   auto optStr2 = make_optional(s2);
 551   ASSERT_TRUE(optStr2.hasValue());
 552   EXPECT_EQ(*optStr2, "abc");
 553   *optStr2 = "cde";
 554   // it's vital to check that s2 wasn't clobbered
 555   EXPECT_EQ(s2, "abc");
 556
 557   // L-value reference version
 558   std::string& s3(s2);
 559   auto optStr3 = make_optional(s3);
 560   ASSERT_TRUE(optStr3.hasValue());
 561   EXPECT_EQ(*optStr3, "abc");
 562   *optStr3 = "cde";
 563   EXPECT_EQ(s3, "abc");
 564
 565   // R-value ref version
 566   unique_ptr<int> pInt(new int(3));
 567   auto optIntPtr = make_optional(std::move(pInt));
 568   EXPECT_TRUE(pInt.get() == nullptr);
 569   ASSERT_TRUE(optIntPtr.hasValue());
 570   EXPECT_EQ(**optIntPtr, 3);
 571 }
 572
 573 #if __CLANG_PREREQ(3, 6)
 574 # pragma clang diagnostic push
 575 # pragma clang diagnostic ignored "-Wself-move"
 576 #endif
 577
 578 TEST(Optional, SelfAssignment) {
 579   Optional<int> a = 42;
 580   a = a;
 581   ASSERT_TRUE(a.hasValue() && a.value() == 42);
 582
 583   Optional<int> b = 23333333;
 584   b = std::move(b);
 585   ASSERT_TRUE(b.hasValue() && b.value() == 23333333);
 586 }
 587
 588 #if __CLANG_PREREQ(3, 6)
 589 # pragma clang diagnostic pop
 590 #endif
 591
 592 class ContainsOptional {
 593  public:
 594   ContainsOptional() { }
 595   explicit ContainsOptional(int x) : opt_(x) { }
 596   bool hasValue() const { return opt_.hasValue(); }
 597   int value() const { return opt_.value(); }
 598
 599   ContainsOptional(const ContainsOptional &other) = default;
 600   ContainsOptional& operator=(const ContainsOptional &other) = default;
 601   ContainsOptional(ContainsOptional &&other) = default;
 602   ContainsOptional& operator=(ContainsOptional &&other) = default;
 603
 604  private:
 605   Optional<int> opt_;
 606 };
 607
 608 /**
 609  * Test that a class containing an Optional can be copy and move assigned.
 610  * This was broken under gcc 4.7 until assignment operators were explicitly
 611  * defined.
 612  */
 613 TEST(Optional, AssignmentContained) {
 614   {
 615     ContainsOptional source(5), target;
 616     target = source;
 617     EXPECT_TRUE(target.hasValue());
 618     EXPECT_EQ(5, target.value());
 619   }
 620
 621   {
 622     ContainsOptional source(5), target;
 623     target = std::move(source);
 624     EXPECT_TRUE(target.hasValue());
 625     EXPECT_EQ(5, target.value());
 626     EXPECT_FALSE(source.hasValue());
 627   }
 628
 629   {
 630     ContainsOptional opt_uninit, target(10);
 631     target = opt_uninit;
 632     EXPECT_FALSE(target.hasValue());
 633   }
 634 }
 635
 636 TEST(Optional, Exceptions) {
 637   Optional<int> empty;
 638   EXPECT_THROW(empty.value(), OptionalEmptyException);
 639 }
 640
 641 TEST(Optional, NoThrowDefaultConstructible) {
 642   EXPECT_TRUE(std::is_nothrow_default_constructible<Optional<bool>>::value);
 643 }
 644
 645 struct NoDestructor {};
 646
 647 struct WithDestructor {
 648   ~WithDestructor();
 649 };
 650
 651 TEST(Optional, TriviallyDestructible) {
 652   // These could all be static_asserts but EXPECT_* give much nicer output on
 653   // failure.
 654   EXPECT_TRUE(std::is_trivially_destructible<Optional<NoDestructor>>::value);
 655   EXPECT_TRUE(std::is_trivially_destructible<Optional<int>>::value);
 656   EXPECT_FALSE(std::is_trivially_destructible<Optional<WithDestructor>>::value);
 657 }
 658
 659 TEST(Optional, Hash) {
 660   // Test it's usable in std::unordered map (compile time check)
 661   std::unordered_map<Optional<int>, Optional<int>> obj;
 662   // Also check the std::hash template can be instantiated by the compiler
 663   std::hash<Optional<int>>()(none);
 664   std::hash<Optional<int>>()(3);
 665 }
 666 }