Export of internal Abseil changes.

--
ac7508120c60dfe689c40929e416b6a486f83ee3 by Gennadiy Rozental <rogeeff@google.com>:

Internal change

PiperOrigin-RevId: 206912089

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bd709faba88565367b6d337466e6456481b5f3e8 by Matt Calabrese <calabrese@google.com>:

Implement `std::experimental::is_detected` in type_traits internals and move `is_detected_convertible` from variant's internals to type_traits internals. This is in preparation of creating workarounds for broken standard traits.

PiperOrigin-RevId: 206825598

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0dbddea569370eb9b6348cee172d1874f9046eb4 by Jorg Brown <jorg@google.com>:

Support users who turn on floating-point conversion warnings

PiperOrigin-RevId: 206813209

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30991f757c8f0100584619d8a9c41897d029f112 by Jorg Brown <jorg@google.com>:

Speed up the absl::Seconds() function for floating-point values, roughly by 4.5x, since
we can take advantage of the fact that we're just taking a floating-point number and
splitting it into its integral and fractional parts.

PiperOrigin-RevId: 206806270

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6883837176838aa5a517e7a8cb4c99afd24c0d12 by Jon Cohen <cohenjon@google.com>:

Remove the DISABLE_INSTALL from absl_container.  It doesn't do anything.

PiperOrigin-RevId: 206802544

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92ab14fed06e6dd1f01a0284bd7f95d3e2c0c3d8 by Jon Cohen <cohenjon@google.com>:

Internal change

PiperOrigin-RevId: 206776244

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17b76c7f364ac562d9e0faeca0320f63aa3fdb85 by Jorg Brown <jorg@google.com>:

Fix absl/strings:numbers_test flakiness due to exceeding the 1-minute timeout

PiperOrigin-RevId: 206763175

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6637843f2e198b8efd90e5577fbc86bdea43b2cc by Abseil Team <absl-team@google.com>:

Adds templated allocator to absl::FixedArray with corresponding tests

PiperOrigin-RevId: 206354178

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bced22f81add828c9b4c60eb45554d36c22e2f96 by Abseil Team <absl-team@google.com>:

Adds templated allocator to absl::FixedArray with corresponding tests

PiperOrigin-RevId: 206347377

--
75be14a71d2d5e335812d5b7670120271fb5bd79 by Abseil Team <absl-team@google.com>:

Internal change.

PiperOrigin-RevId: 206326935

--
6929e43f4c7898b1f51e441911a19092a06fbf97 by Abseil Team <absl-team@google.com>:

Adds templated allocator to absl::FixedArray with corresponding tests

PiperOrigin-RevId: 206326368

--
55ae34b75ff029eb267f9519e577bab8a575b487 by Abseil Team <absl-team@google.com>:

Internal change.

PiperOrigin-RevId: 206233448

--
6950a8ccddf35d451eec2d02cd28a797c8b7cf6a by Matt Kulukundis <kfm@google.com>:

Internal change

PiperOrigin-RevId: 206035613
GitOrigin-RevId: ac7508120c60dfe689c40929e416b6a486f83ee3
Change-Id: I675605abbedab6b3ac9aa82195cbd059ff7c82b1

2 files changed, 123 insertions, 2 deletions

diff --git a/absl/meta/type_traits.h b/absl/meta/type_traits.h
index 8d3264f1..457b8908 100644
--- a/absl/meta/type_traits.h
+++ b/absl/meta/type_traits.h
@@ -44,6 +44,7 @@
 namespace absl {
 
 namespace type_traits_internal {
+
 template <typename... Ts>
 struct VoidTImpl {
   using type = void;
@@ -61,6 +62,49 @@ struct default_alignment_of_aligned_storage<Len,
   static constexpr size_t value = Align;
 };
 
+////////////////////////////////
+// Library Fundamentals V2 TS //
+////////////////////////////////
+
+// NOTE: The `is_detected` family of templates here differ from the library
+// fundamentals specification in that for library fundamentals, `Op<Args...>` is
+// evaluated as soon as the type `is_detected<Op, Args...>` undergoes
+// substitution, regardless of whether or not the `::value` is accessed. That
+// is inconsistent with all other standard traits and prevents lazy evaluation
+// in larger contexts (such as if the `is_detected` check is a trailing argument
+// of a `conjunction`. This implementation opts to instead be lazy in the same
+// way that the standard traits are (this "defect" of the detection idiom
+// specifications has been reported).
+
+template <class Enabler, template <class...> class Op, class... Args>
+struct is_detected_impl {
+  using type = std::false_type;
+};
+
+template <template <class...> class Op, class... Args>
+struct is_detected_impl<typename VoidTImpl<Op<Args...>>::type, Op, Args...> {
+  using type = std::true_type;
+};
+
+template <template <class...> class Op, class... Args>
+struct is_detected : is_detected_impl<void, Op, Args...>::type {};
+
+template <class Enabler, class To, template <class...> class Op, class... Args>
+struct is_detected_convertible_impl {
+  using type = std::false_type;
+};
+
+template <class To, template <class...> class Op, class... Args>
+struct is_detected_convertible_impl<
+    typename std::enable_if<std::is_convertible<Op<Args...>, To>::value>::type,
+    To, Op, Args...> {
+  using type = std::true_type;
+};
+
+template <class To, template <class...> class Op, class... Args>
+struct is_detected_convertible
+    : is_detected_convertible_impl<void, To, Op, Args...>::type {};
+
 }  // namespace type_traits_internal
 
 // void_t()
diff --git a/absl/meta/type_traits_test.cc b/absl/meta/type_traits_test.cc
index 9dd95429..81b4bd32 100644
--- a/absl/meta/type_traits_test.cc
+++ b/absl/meta/type_traits_test.cc
@@ -34,6 +34,83 @@ struct simple_pair {
 
 struct Dummy {};
 
+struct ReturnType {};
+struct ConvertibleToReturnType {
+  operator ReturnType() const;  // NOLINT
+};
+
+// Unique types used as parameter types for testing the detection idiom.
+struct StructA {};
+struct StructB {};
+struct StructC {};
+
+struct TypeWithBarFunction {
+  template <class T,
+            absl::enable_if_t<std::is_same<T&&, StructA&>::value, int> = 0>
+  ReturnType bar(T&&, const StructB&, StructC&&) &&;  // NOLINT
+};
+
+struct TypeWithBarFunctionAndConvertibleReturnType {
+  template <class T,
+            absl::enable_if_t<std::is_same<T&&, StructA&>::value, int> = 0>
+  ConvertibleToReturnType bar(T&&, const StructB&, StructC&&) &&;  // NOLINT
+};
+
+template <class Class, class... Ts>
+using BarIsCallableImpl =
+    decltype(std::declval<Class>().bar(std::declval<Ts>()...));
+
+template <class Class, class... T>
+using BarIsCallable =
+    absl::type_traits_internal::is_detected<BarIsCallableImpl, Class, T...>;
+
+template <class Class, class... T>
+using BarIsCallableConv = absl::type_traits_internal::is_detected_convertible<
+    ReturnType, BarIsCallableImpl, Class, T...>;
+
+// NOTE: Test of detail type_traits_internal::is_detected.
+TEST(IsDetectedTest, BasicUsage) {
+  EXPECT_TRUE((BarIsCallable<TypeWithBarFunction, StructA&, const StructB&,
+                             StructC>::value));
+  EXPECT_TRUE(
+      (BarIsCallable<TypeWithBarFunction, StructA&, StructB&, StructC>::value));
+  EXPECT_TRUE(
+      (BarIsCallable<TypeWithBarFunction, StructA&, StructB, StructC>::value));
+
+  EXPECT_FALSE((BarIsCallable<int, StructA&, const StructB&, StructC>::value));
+  EXPECT_FALSE((BarIsCallable<TypeWithBarFunction&, StructA&, const StructB&,
+                              StructC>::value));
+  EXPECT_FALSE((BarIsCallable<TypeWithBarFunction, StructA, const StructB&,
+                              StructC>::value));
+}
+
+// NOTE: Test of detail type_traits_internal::is_detected_convertible.
+TEST(IsDetectedConvertibleTest, BasicUsage) {
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, const StructB&,
+                                 StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, StructB&,
+                                 StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, StructB,
+                                 StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
+                                 StructA&, const StructB&, StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
+                                 StructA&, StructB&, StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
+                                 StructA&, StructB, StructC>::value));
+
+  EXPECT_FALSE(
+      (BarIsCallableConv<int, StructA&, const StructB&, StructC>::value));
+  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunction&, StructA&,
+                                  const StructB&, StructC>::value));
+  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunction, StructA, const StructB&,
+                                  StructC>::value));
+  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType&,
+                                  StructA&, const StructB&, StructC>::value));
+  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
+                                  StructA, const StructB&, StructC>::value));
+}
+
 TEST(VoidTTest, BasicUsage) {
   StaticAssertTypeEq<void, absl::void_t<Dummy>>();
   StaticAssertTypeEq<void, absl::void_t<Dummy, Dummy, Dummy>>();
@@ -718,8 +795,8 @@ TEST(TypeTraitsTest, TestDecay) {
   ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int[][1]);
 
   ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int());
-  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int(float));
-  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int(char, ...));
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int(float));  // NOLINT
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int(char, ...));  // NOLINT
 }
 
 struct TypeA {};