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 private:
 128   friend bool operator==(const MoveTester& o1, const MoveTester& o2);
 129   std::string s_;
 130 };
 131
 132 bool operator==(const MoveTester& o1, const MoveTester& o2) {
 133   return o1.s_ == o2.s_;
 134 }
 135
 136 TEST(Optional, value_or_rvalue_arg) {
 137   Optional<MoveTester> opt;
 138   MoveTester dflt = "hello";
 139   EXPECT_EQ("hello", opt.value_or(dflt));
 140   EXPECT_EQ("hello", dflt);
 141   EXPECT_EQ("hello", opt.value_or(std::move(dflt)));
 142   EXPECT_EQ("", dflt);
 143   EXPECT_EQ("world", opt.value_or("world"));
 144
 145   dflt = "hello";
 146   // Make sure that the const overload works on const objects
 147   const auto& optc = opt;
 148   EXPECT_EQ("hello", optc.value_or(dflt));
 149   EXPECT_EQ("hello", dflt);
 150   EXPECT_EQ("hello", optc.value_or(std::move(dflt)));
 151   EXPECT_EQ("", dflt);
 152   EXPECT_EQ("world", optc.value_or("world"));
 153
 154   dflt = "hello";
 155   opt = "meow";
 156   EXPECT_EQ("meow", opt.value_or(dflt));
 157   EXPECT_EQ("hello", dflt);
 158   EXPECT_EQ("meow", opt.value_or(std::move(dflt)));
 159   EXPECT_EQ("hello", dflt);  // only moved if used
 160 }
 161
 162 TEST(Optional, value_or_noncopyable) {
 163   Optional<std::unique_ptr<int>> opt;
 164   std::unique_ptr<int> dflt(new int(42));
 165   EXPECT_EQ(42, *std::move(opt).value_or(std::move(dflt)));
 166 }
 167
 168 struct ExpectingDeleter {
 169   explicit ExpectingDeleter(int expected) : expected(expected) { }
 170   int expected;
 171   void operator()(const int* ptr) {
 172     EXPECT_EQ(*ptr, expected);
 173     delete ptr;
 174   }
 175 };
 176
 177 TEST(Optional, value_move) {
 178   auto ptr = Optional<std::unique_ptr<int, ExpectingDeleter>>(
 179       {new int(42), ExpectingDeleter{1337}}).value();
 180   *ptr = 1337;
 181 }
 182
 183 TEST(Optional, dereference_move) {
 184   auto ptr = *Optional<std::unique_ptr<int, ExpectingDeleter>>(
 185       {new int(42), ExpectingDeleter{1337}});
 186   *ptr = 1337;
 187 }
 188
 189 TEST(Optional, EmptyConstruct) {
 190   Optional<int> opt;
 191   EXPECT_FALSE(bool(opt));
 192   Optional<int> test1(opt);
 193   EXPECT_FALSE(bool(test1));
 194   Optional<int> test2(std::move(opt));
 195   EXPECT_FALSE(bool(test2));
 196 }
 197
 198 TEST(Optional, InPlaceConstruct) {
 199   using A = std::pair<int, double>;
 200   Optional<A> opt(in_place, 5, 3.2);
 201   EXPECT_TRUE(bool(opt));
 202   EXPECT_EQ(5, opt->first);
 203 }
 204
 205 TEST(Optional, InPlaceNestedConstruct) {
 206   using A = std::pair<int, double>;
 207   Optional<Optional<A>> opt(in_place, in_place, 5, 3.2);
 208   EXPECT_TRUE(bool(opt));
 209   EXPECT_TRUE(bool(*opt));
 210   EXPECT_EQ(5, (*opt)->first);
 211 }
 212
 213 TEST(Optional, Unique) {
 214   Optional<unique_ptr<int>> opt;
 215
 216   opt.clear();
 217   EXPECT_FALSE(bool(opt));
 218   // empty->emplaced
 219   opt.emplace(new int(5));
 220   EXPECT_TRUE(bool(opt));
 221   EXPECT_EQ(5, **opt);
 222
 223   opt.clear();
 224   // empty->moved
 225   opt = unique_ptr<int>(new int(6));
 226   EXPECT_EQ(6, **opt);
 227   // full->moved
 228   opt = unique_ptr<int>(new int(7));
 229   EXPECT_EQ(7, **opt);
 230
 231   // move it out by move construct
 232   Optional<unique_ptr<int>> moved(std::move(opt));
 233   EXPECT_TRUE(bool(moved));
 234   EXPECT_FALSE(bool(opt));
 235   EXPECT_EQ(7, **moved);
 236
 237   EXPECT_TRUE(bool(moved));
 238   opt = std::move(moved); // move it back by move assign
 239   EXPECT_FALSE(bool(moved));
 240   EXPECT_TRUE(bool(opt));
 241   EXPECT_EQ(7, **opt);
 242 }
 243
 244 TEST(Optional, Shared) {
 245   shared_ptr<int> ptr;
 246   Optional<shared_ptr<int>> opt;
 247   EXPECT_FALSE(bool(opt));
 248   // empty->emplaced
 249   opt.emplace(new int(5));
 250   EXPECT_TRUE(bool(opt));
 251   ptr = opt.value();
 252   EXPECT_EQ(ptr.get(), opt->get());
 253   EXPECT_EQ(2, ptr.use_count());
 254   opt.clear();
 255   EXPECT_EQ(1, ptr.use_count());
 256   // full->copied
 257   opt = ptr;
 258   EXPECT_EQ(2, ptr.use_count());
 259   EXPECT_EQ(ptr.get(), opt->get());
 260   opt.clear();
 261   EXPECT_EQ(1, ptr.use_count());
 262   // full->moved
 263   opt = std::move(ptr);
 264   EXPECT_EQ(1, opt->use_count());
 265   EXPECT_EQ(nullptr, ptr.get());
 266   {
 267     Optional<shared_ptr<int>> copied(opt);
 268     EXPECT_EQ(2, opt->use_count());
 269     Optional<shared_ptr<int>> moved(std::move(opt));
 270     EXPECT_EQ(2, moved->use_count());
 271     moved.emplace(new int(6));
 272     EXPECT_EQ(1, moved->use_count());
 273     copied = moved;
 274     EXPECT_EQ(2, moved->use_count());
 275   }
 276 }
 277
 278 TEST(Optional, Order) {
 279   std::vector<Optional<int>> vect{
 280     { none },
 281     { 3 },
 282     { 1 },
 283     { none },
 284     { 2 },
 285   };
 286   std::vector<Optional<int>> expected {
 287     { none },
 288     { none },
 289     { 1 },
 290     { 2 },
 291     { 3 },
 292   };
 293   std::sort(vect.begin(), vect.end());
 294   EXPECT_EQ(vect, expected);
 295 }
 296
 297 TEST(Optional, Swap) {
 298   Optional<std::string> a;
 299   Optional<std::string> b;
 300
 301   swap(a, b);
 302   EXPECT_FALSE(a.hasValue());
 303   EXPECT_FALSE(b.hasValue());
 304
 305   a = "hello";
 306   EXPECT_TRUE(a.hasValue());
 307   EXPECT_FALSE(b.hasValue());
 308   EXPECT_EQ("hello", a.value());
 309
 310   swap(a, b);
 311   EXPECT_FALSE(a.hasValue());
 312   EXPECT_TRUE(b.hasValue());
 313   EXPECT_EQ("hello", b.value());
 314
 315   a = "bye";
 316   EXPECT_TRUE(a.hasValue());
 317   EXPECT_EQ("bye", a.value());
 318
 319   swap(a, b);
 320 }
 321
 322 TEST(Optional, Comparisons) {
 323   Optional<int> o_;
 324   Optional<int> o1(1);
 325   Optional<int> o2(2);
 326
 327   EXPECT_TRUE(o_ <= (o_));
 328   EXPECT_TRUE(o_ == (o_));
 329   EXPECT_TRUE(o_ >= (o_));
 330
 331   EXPECT_TRUE(o1 < o2);
 332   EXPECT_TRUE(o1 <= o2);
 333   EXPECT_TRUE(o1 <= (o1));
 334   EXPECT_TRUE(o1 == (o1));
 335   EXPECT_TRUE(o1 != o2);
 336   EXPECT_TRUE(o1 >= (o1));
 337   EXPECT_TRUE(o2 >= o1);
 338   EXPECT_TRUE(o2 > o1);
 339
 340   EXPECT_FALSE(o2 < o1);
 341   EXPECT_FALSE(o2 <= o1);
 342   EXPECT_FALSE(o2 <= o1);
 343   EXPECT_FALSE(o2 == o1);
 344   EXPECT_FALSE(o1 != (o1));
 345   EXPECT_FALSE(o1 >= o2);
 346   EXPECT_FALSE(o1 >= o2);
 347   EXPECT_FALSE(o1 > o2);
 348
 349   /* folly::Optional explicitly doesn't support comparisons with contained value
 350   EXPECT_TRUE(1 < o2);
 351   EXPECT_TRUE(1 <= o2);
 352   EXPECT_TRUE(1 <= o1);
 353   EXPECT_TRUE(1 == o1);
 354   EXPECT_TRUE(2 != o1);
 355   EXPECT_TRUE(1 >= o1);
 356   EXPECT_TRUE(2 >= o1);
 357   EXPECT_TRUE(2 > o1);
 358
 359   EXPECT_FALSE(o2 < 1);
 360   EXPECT_FALSE(o2 <= 1);
 361   EXPECT_FALSE(o2 <= 1);
 362   EXPECT_FALSE(o2 == 1);
 363   EXPECT_FALSE(o2 != 2);
 364   EXPECT_FALSE(o1 >= 2);
 365   EXPECT_FALSE(o1 >= 2);
 366   EXPECT_FALSE(o1 > 2);
 367   */
 368
 369   // boost::optional does support comparison with contained value, which can
 370   // lead to confusion when a bool is contained
 371   boost::optional<int> boi(3);
 372   EXPECT_TRUE(boi < 5);
 373   EXPECT_TRUE(boi <= 4);
 374   EXPECT_TRUE(boi == 3);
 375   EXPECT_TRUE(boi != 2);
 376   EXPECT_TRUE(boi >= 1);
 377   EXPECT_TRUE(boi > 0);
 378   EXPECT_TRUE(1 <  boi);
 379   EXPECT_TRUE(2 <= boi);
 380   EXPECT_TRUE(3 == boi);
 381   EXPECT_TRUE(4 != boi);
 382   EXPECT_TRUE(5 >= boi);
 383   EXPECT_TRUE(6 >  boi);
 384
 385   boost::optional<bool> bob(false);
 386   EXPECT_TRUE((bool)bob);
 387   EXPECT_TRUE(bob == false); // well that was confusing
 388   EXPECT_FALSE(bob != false);
 389 }
 390
 391 TEST(Optional, HeterogeneousComparisons) {
 392   using opt8 = Optional<uint8_t>;
 393   using opt64 = Optional<uint64_t>;
 394
 395   EXPECT_TRUE(opt8(4) == uint64_t(4));
 396   EXPECT_FALSE(opt8(8) == uint64_t(4));
 397   EXPECT_FALSE(opt8() == uint64_t(4));
 398
 399   EXPECT_TRUE(uint64_t(4) == opt8(4));
 400   EXPECT_FALSE(uint64_t(4) == opt8(8));
 401   EXPECT_FALSE(uint64_t(4) == opt8());
 402
 403   EXPECT_FALSE(opt8(4) != uint64_t(4));
 404   EXPECT_TRUE(opt8(8) != uint64_t(4));
 405   EXPECT_TRUE(opt8() != uint64_t(4));
 406
 407   EXPECT_FALSE(uint64_t(4) != opt8(4));
 408   EXPECT_TRUE(uint64_t(4) != opt8(8));
 409   EXPECT_TRUE(uint64_t(4) != opt8());
 410
 411   EXPECT_TRUE(opt8() == opt64());
 412   EXPECT_TRUE(opt8(4) == opt64(4));
 413   EXPECT_FALSE(opt8(8) == opt64(4));
 414   EXPECT_FALSE(opt8() == opt64(4));
 415   EXPECT_FALSE(opt8(4) == opt64());
 416
 417   EXPECT_FALSE(opt8() != opt64());
 418   EXPECT_FALSE(opt8(4) != opt64(4));
 419   EXPECT_TRUE(opt8(8) != opt64(4));
 420   EXPECT_TRUE(opt8() != opt64(4));
 421   EXPECT_TRUE(opt8(4) != opt64());
 422
 423   EXPECT_TRUE(opt8() < opt64(4));
 424   EXPECT_TRUE(opt8(4) < opt64(8));
 425   EXPECT_FALSE(opt8() < opt64());
 426   EXPECT_FALSE(opt8(4) < opt64(4));
 427   EXPECT_FALSE(opt8(8) < opt64(4));
 428   EXPECT_FALSE(opt8(4) < opt64());
 429
 430   EXPECT_FALSE(opt8() > opt64(4));
 431   EXPECT_FALSE(opt8(4) > opt64(8));
 432   EXPECT_FALSE(opt8() > opt64());
 433   EXPECT_FALSE(opt8(4) > opt64(4));
 434   EXPECT_TRUE(opt8(8) > opt64(4));
 435   EXPECT_TRUE(opt8(4) > opt64());
 436
 437   EXPECT_TRUE(opt8() <= opt64(4));
 438   EXPECT_TRUE(opt8(4) <= opt64(8));
 439   EXPECT_TRUE(opt8() <= opt64());
 440   EXPECT_TRUE(opt8(4) <= opt64(4));
 441   EXPECT_FALSE(opt8(8) <= opt64(4));
 442   EXPECT_FALSE(opt8(4) <= opt64());
 443
 444   EXPECT_FALSE(opt8() >= opt64(4));
 445   EXPECT_FALSE(opt8(4) >= opt64(8));
 446   EXPECT_TRUE(opt8() >= opt64());
 447   EXPECT_TRUE(opt8(4) >= opt64(4));
 448   EXPECT_TRUE(opt8(8) >= opt64(4));
 449   EXPECT_TRUE(opt8(4) >= opt64());
 450 }
 451
 452 TEST(Optional, Conversions) {
 453   Optional<bool> mbool;
 454   Optional<short> mshort;
 455   Optional<char*> mstr;
 456   Optional<int> mint;
 457
 458   //These don't compile
 459   //bool b = mbool;
 460   //short s = mshort;
 461   //char* c = mstr;
 462   //int x = mint;
 463   //char* c(mstr);
 464   //short s(mshort);
 465   //int x(mint);
 466
 467   // intended explicit operator bool, for if (opt).
 468   bool b(mbool);
 469   EXPECT_FALSE(b);
 470
 471   // Truthy tests work and are not ambiguous
 472   if (mbool && mshort && mstr && mint) { // only checks not-empty
 473     if (*mbool && *mshort && *mstr && *mint) { // only checks value
 474       ;
 475     }
 476   }
 477
 478   mbool = false;
 479   EXPECT_TRUE(bool(mbool));
 480   EXPECT_FALSE(*mbool);
 481
 482   mbool = true;
 483   EXPECT_TRUE(bool(mbool));
 484   EXPECT_TRUE(*mbool);
 485
 486   mbool = none;
 487   EXPECT_FALSE(bool(mbool));
 488
 489   // No conversion allowed; does not compile
 490   // EXPECT_TRUE(mbool == false);
 491 }
 492
 493 TEST(Optional, Pointee) {
 494   Optional<int> x;
 495   EXPECT_FALSE(get_pointer(x));
 496   x = 1;
 497   EXPECT_TRUE(get_pointer(x));
 498   *get_pointer(x) = 2;
 499   EXPECT_TRUE(*x == 2);
 500   x = none;
 501   EXPECT_FALSE(get_pointer(x));
 502 }
 503
 504 TEST(Optional, MakeOptional) {
 505   // const L-value version
 506   const std::string s("abc");
 507   auto optStr = make_optional(s);
 508   ASSERT_TRUE(optStr.hasValue());
 509   EXPECT_EQ(*optStr, "abc");
 510   *optStr = "cde";
 511   EXPECT_EQ(s, "abc");
 512   EXPECT_EQ(*optStr, "cde");
 513
 514   // L-value version
 515   std::string s2("abc");
 516   auto optStr2 = make_optional(s2);
 517   ASSERT_TRUE(optStr2.hasValue());
 518   EXPECT_EQ(*optStr2, "abc");
 519   *optStr2 = "cde";
 520   // it's vital to check that s2 wasn't clobbered
 521   EXPECT_EQ(s2, "abc");
 522
 523   // L-value reference version
 524   std::string& s3(s2);
 525   auto optStr3 = make_optional(s3);
 526   ASSERT_TRUE(optStr3.hasValue());
 527   EXPECT_EQ(*optStr3, "abc");
 528   *optStr3 = "cde";
 529   EXPECT_EQ(s3, "abc");
 530
 531   // R-value ref version
 532   unique_ptr<int> pInt(new int(3));
 533   auto optIntPtr = make_optional(std::move(pInt));
 534   EXPECT_TRUE(pInt.get() == nullptr);
 535   ASSERT_TRUE(optIntPtr.hasValue());
 536   EXPECT_EQ(**optIntPtr, 3);
 537 }
 538
 539 #if __CLANG_PREREQ(3, 6)
 540 # pragma clang diagnostic push
 541 # pragma clang diagnostic ignored "-Wself-move"
 542 #endif
 543
 544 TEST(Optional, SelfAssignment) {
 545   Optional<int> a = 42;
 546   a = a;
 547   ASSERT_TRUE(a.hasValue() && a.value() == 42);
 548
 549   Optional<int> b = 23333333;
 550   b = std::move(b);
 551   ASSERT_TRUE(b.hasValue() && b.value() == 23333333);
 552 }
 553
 554 #if __CLANG_PREREQ(3, 6)
 555 # pragma clang diagnostic pop
 556 #endif
 557
 558 class ContainsOptional {
 559  public:
 560   ContainsOptional() { }
 561   explicit ContainsOptional(int x) : opt_(x) { }
 562   bool hasValue() const { return opt_.hasValue(); }
 563   int value() const { return opt_.value(); }
 564
 565   ContainsOptional(const ContainsOptional &other) = default;
 566   ContainsOptional& operator=(const ContainsOptional &other) = default;
 567   ContainsOptional(ContainsOptional &&other) = default;
 568   ContainsOptional& operator=(ContainsOptional &&other) = default;
 569
 570  private:
 571   Optional<int> opt_;
 572 };
 573
 574 /**
 575  * Test that a class containing an Optional can be copy and move assigned.
 576  * This was broken under gcc 4.7 until assignment operators were explicitly
 577  * defined.
 578  */
 579 TEST(Optional, AssignmentContained) {
 580   {
 581     ContainsOptional source(5), target;
 582     target = source;
 583     EXPECT_TRUE(target.hasValue());
 584     EXPECT_EQ(5, target.value());
 585   }
 586
 587   {
 588     ContainsOptional source(5), target;
 589     target = std::move(source);
 590     EXPECT_TRUE(target.hasValue());
 591     EXPECT_EQ(5, target.value());
 592     EXPECT_FALSE(source.hasValue());
 593   }
 594
 595   {
 596     ContainsOptional opt_uninit, target(10);
 597     target = opt_uninit;
 598     EXPECT_FALSE(target.hasValue());
 599   }
 600 }
 601
 602 TEST(Optional, Exceptions) {
 603   Optional<int> empty;
 604   EXPECT_THROW(empty.value(), OptionalEmptyException);
 605 }
 606
 607 TEST(Optional, NoThrowDefaultConstructible) {
 608   EXPECT_TRUE(std::is_nothrow_default_constructible<Optional<bool>>::value);
 609 }
 610
 611 struct NoDestructor {};
 612
 613 struct WithDestructor {
 614   ~WithDestructor();
 615 };
 616
 617 TEST(Optional, TriviallyDestructible) {
 618   // These could all be static_asserts but EXPECT_* give much nicer output on
 619   // failure.
 620   EXPECT_TRUE(std::is_trivially_destructible<Optional<NoDestructor>>::value);
 621   EXPECT_TRUE(std::is_trivially_destructible<Optional<int>>::value);
 622   EXPECT_FALSE(std::is_trivially_destructible<Optional<WithDestructor>>::value);
 623 }
 624
 625 TEST(Optional, Hash) {
 626   // Test it's usable in std::unordered map (compile time check)
 627   std::unordered_map<Optional<int>, Optional<int>> obj;
 628   // Also check the std::hash template can be instantiated by the compiler
 629   std::hash<Optional<int>>()(none);
 630   std::hash<Optional<int>>()(3);
 631 }
 632 }