Add internal traits to absl::Span for lifetimebound detection

PiperOrigin-RevId: 621169753
Change-Id: Ib6d7b248e14f29f1f91c24b8e1cf9703962b0e36

absl/types/BUILD.bazel

@@ -138,6 +138,7 @@ cc_test(
         "//absl/container:fixed_array",
         "//absl/container:inlined_vector",
         "//absl/hash:hash_testing",
+        "//absl/meta:type_traits",
         "//absl/strings",
         "@com_google_googletest//:gtest",
         "@com_google_googletest//:gtest_main",

absl/types/CMakeLists.txt

@@ -138,6 +138,7 @@ absl_cc_test(
     absl::inlined_vector
     absl::hash_testing
     absl::strings
+    absl::type_traits
     GTest::gmock_main
 )
 

absl/types/span.h

@@ -185,6 +185,7 @@ class Span {
   using const_reverse_iterator = std::reverse_iterator<const_iterator>;
   using size_type = size_t;
   using difference_type = ptrdiff_t;
+  using absl_internal_is_view = std::true_type;
 
   static const size_type npos = ~(size_type(0));
 

absl/types/span_test.cc

@@ -31,10 +31,15 @@
 #include "absl/container/fixed_array.h"
 #include "absl/container/inlined_vector.h"
 #include "absl/hash/hash_testing.h"
+#include "absl/meta/type_traits.h"
 #include "absl/strings/str_cat.h"
 
 namespace {
 
+static_assert(!absl::type_traits_internal::IsOwner<absl::Span<int>>::value &&
+                  absl::type_traits_internal::IsView<absl::Span<int>>::value,
+              "Span is a view, not an owner");
+
 MATCHER_P(DataIs, data,
           absl::StrCat("data() ", negation ? "isn't " : "is ",
                        testing::PrintToString(data))) {