Improving flat containers interface.

base/template_util_unittest.cc

Index: base/template_util_unittest.cc
diff --git a/base/template_util_unittest.cc b/base/template_util_unittest.cc
index 70d28c8e4e2806fdbcb48cc7402ac75ba2c5c117..f7db2548458027cf110a4c8b3365e78ae72610db 100644
--- a/base/template_util_unittest.cc
+++ b/base/template_util_unittest.cc
@@ -6,6 +6,8 @@
 
 #include <string>
 
+#include "base/containers/flat_tree.h"
+#include "base/test/move_only_int.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ -70,4 +72,14 @@ static_assert(
     "struct with operator<< should be printable by const ref");
 
 }  // namespace
+
+TEST(Functors, Less) {
+  using ExplicitInt = base::MoveOnlyInt;
+  EXPECT_TRUE(base::less()(ExplicitInt(3), 4));
+  EXPECT_FALSE(base::less()(4, ExplicitInt(3)));
+  EXPECT_TRUE(base::less()(3, 4));
+
+  static_assert(base::internal::IsTransparentCompare<base::less>::value, "");
+}
+
 }  // namespace base