diff options
Diffstat (limited to 'absl/types/optional_test.cc')
-rw-r--r-- | absl/types/optional_test.cc | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/absl/types/optional_test.cc b/absl/types/optional_test.cc index 25b44b171c9d..65f43871e1c0 100644 --- a/absl/types/optional_test.cc +++ b/absl/types/optional_test.cc @@ -24,6 +24,17 @@ #include "absl/meta/type_traits.h" #include "absl/strings/string_view.h" +struct Hashable {}; + +namespace std { +template <> +struct hash<Hashable> { + size_t operator()(const Hashable&) { return 0; } +}; +} // namespace std + +struct NonHashable {}; + namespace { std::string TypeQuals(std::string&) { return "&"; } @@ -1434,6 +1445,17 @@ TEST(optionalTest, ValueType) { (std::is_same<absl::optional<int>::value_type, absl::nullopt_t>::value)); } +template <typename T> +struct is_hash_enabled_for { + template <typename U, typename = decltype(std::hash<U>()(std::declval<U>()))> + static std::true_type test(int); + + template <typename U> + static std::false_type test(...); + + static constexpr bool value = decltype(test<T>(0))::value; +}; + TEST(optionalTest, Hash) { std::hash<absl::optional<int>> hash; std::set<size_t> hashcodes; @@ -1442,6 +1464,34 @@ TEST(optionalTest, Hash) { hashcodes.insert(hash(i)); } EXPECT_GT(hashcodes.size(), 90); + + static_assert(is_hash_enabled_for<absl::optional<int>>::value, ""); + static_assert(is_hash_enabled_for<absl::optional<Hashable>>::value, ""); + +#if defined(_MSC_VER) || (defined(_LIBCPP_VERSION) && \ + _LIBCPP_VERSION < 4000 && _LIBCPP_STD_VER > 11) + // For MSVC and libc++ (< 4.0 and c++14), std::hash primary template has a + // static_assert to catch any user-defined type that doesn't provide a hash + // specialization. So instantiating std::hash<absl::optional<T>> will result + // in a hard error which is not SFINAE friendly. +#define ABSL_STD_HASH_NOT_SFINAE_FRIENDLY 1 +#endif + +#ifndef ABSL_STD_HASH_NOT_SFINAE_FRIENDLY + static_assert(!is_hash_enabled_for<absl::optional<NonHashable>>::value, ""); +#endif + + // libstdc++ std::optional is missing remove_const_t, i.e. it's using + // std::hash<T> rather than std::hash<std::remove_const_t<T>>. + // Reference: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82262 +#ifndef __GLIBCXX__ + static_assert(is_hash_enabled_for<absl::optional<const int>>::value, ""); + static_assert(is_hash_enabled_for<absl::optional<const Hashable>>::value, ""); + std::hash<absl::optional<const int>> c_hash; + for (int i = 0; i < 100; ++i) { + EXPECT_EQ(hash(i), c_hash(i)); + } +#endif } struct MoveMeNoThrow { |