Export of internal Abseil changes

--
f2ffea8ae1c1b152b63bf561375cfb6eb6b9dbe5 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 432180490
Change-Id: I5e318e1d06fe26eee08920fe39f8a6285eb8e217

--
e5d0de4b3293833eab3f77252a091ac4ed74b210 by Derek Mauro <dmauro@google.com>:

absl::optional - Add a workaround for an internal compiler error in GCC5 though GCC10

PiperOrigin-RevId: 432047437
Change-Id: I524a9098dadc116d8a423dd66f7ec5ee894f2874
GitOrigin-RevId: f2ffea8ae1c1b152b63bf561375cfb6eb6b9dbe5

1 files changed, 26 insertions, 0 deletions

diff --git a/absl/types/optional_test.cc b/absl/types/optional_test.cc
index 7ef142cb..1846e695 100644
--- a/absl/types/optional_test.cc
+++ b/absl/types/optional_test.cc
@@ -27,6 +27,32 @@
 #include "absl/meta/type_traits.h"
 #include "absl/strings/string_view.h"
 
+// The following types help test an internal compiler error in GCC5 though
+// GCC10. The case OptionalTest.InternalCompilerErrorInGcc5ToGcc10 crashes the
+// compiler without a workaround. This test case should remain at the beginning
+// of the file as the internal compiler error is sensitive to other constructs
+// in this file.
+template <class T, class...>
+using GccIceHelper1 = T;
+template <typename T>
+struct GccIceHelper2 {};
+template <typename T>
+class GccIce {
+  template <typename U,
+            typename SecondTemplateArgHasToExistForSomeReason = void,
+            typename DependentType = void,
+            typename = std::is_assignable<GccIceHelper1<T, DependentType>&, U>>
+  GccIce& operator=(GccIceHelper2<U> const&) {}
+};
+
+TEST(OptionalTest, InternalCompilerErrorInGcc5ToGcc10) {
+  GccIce<int> instantiate_ice_with_same_type_as_optional;
+  static_cast<void>(instantiate_ice_with_same_type_as_optional);
+  absl::optional<int> val1;
+  absl::optional<int> val2;
+  val1 = val2;
+}
+
 struct Hashable {};
 
 namespace std {