base: Support using (D)CHECK on scoped enums.

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 5686d7c752d04c04771b0ee741984490de5778cc..057d7dc5bcf96646208654ec1a58a59ef8a67ed3 100644
--- a/base/template_util_unittest.cc
+++ b/base/template_util_unittest.cc
@@ -4,11 +4,26 @@
 
 #include "base/template_util.h"
 
+#include <string>
+
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 namespace {
 
+enum SimpleEnum { SIMPLE_ENUM };
+enum EnumWithExplicitType : uint64_t { ENUM_WITH_EXPLICIT_TYPE };
+enum class ScopedEnum { SCOPED_ENUM };
+enum class ScopedEnumWithOperator { SCOPED_ENUM_WITH_OPERATOR };
+std::ostream& operator<<(std::ostream& os, ScopedEnumWithOperator v) {
+  return os;
+}
+struct SimpleStruct {};
+struct StructWithOperator {};
+std::ostream& operator<<(std::ostream& os, const StructWithOperator& v) {
+  return os;
+}
+
 // is_non_const_reference<Type>
 static_assert(!is_non_const_reference<int>::value, "IsNonConstReference");
 static_assert(!is_non_const_reference<const int&>::value,
@@ -48,5 +63,53 @@ static_assert(is_move_assignable<AssignCopy>::value, "IsMoveAssignable");
 static_assert(is_move_assignable<AssignNoCopy>::value, "IsMoveAssignable");
 static_assert(!is_move_assignable<AssignNoMove>::value, "IsMoveAssignable");
 
+// A few standard types that definitely support printing.
+static_assert(internal::SupportsOstreamOperator<int>::value,
+              "ints should be printable");
+static_assert(internal::SupportsOstreamOperator<const char*>::value,
+              "C strings should be printable");
+static_assert(internal::SupportsOstreamOperator<std::string>::value,
+              "std::string should be printable");
+
+// Various kinds of enums operator<< support.
+static_assert(internal::SupportsOstreamOperator<SimpleEnum>::value,
+              "simple enum should be printable by value");
+static_assert(internal::SupportsOstreamOperator<const SimpleEnum&>::value,
+              "simple enum should be printable by const ref");
+static_assert(internal::SupportsOstreamOperator<EnumWithExplicitType>::value,
+              "enum with explicit type should be printable by value");
+static_assert(
+    internal::SupportsOstreamOperator<const EnumWithExplicitType&>::value,
+    "enum with explicit type should be printable by const ref");
+static_assert(!internal::SupportsOstreamOperator<ScopedEnum>::value,
+              "scoped enum should not be printable by value");
+static_assert(!internal::SupportsOstreamOperator<const ScopedEnum&>::value,
+              "simple enum should not be printable by const ref");
+static_assert(internal::SupportsOstreamOperator<ScopedEnumWithOperator>::value,
+              "scoped enum with operator<< should be printable by value");
+static_assert(
+    internal::SupportsOstreamOperator<const ScopedEnumWithOperator&>::value,
+    "scoped enum with operator<< should be printable by const ref");
+
+// operator<< support on structs.
+static_assert(!internal::SupportsOstreamOperator<SimpleStruct>::value,
+              "simple struct should not be printable by value");
+static_assert(!internal::SupportsOstreamOperator<const SimpleStruct&>::value,
+              "simple struct should not be printable by const ref");
+static_assert(internal::SupportsOstreamOperator<StructWithOperator>::value,
+              "struct with operator<< should be printable by value");
+static_assert(
+    internal::SupportsOstreamOperator<const StructWithOperator&>::value,
+    "struct with operator<< should be printable by const ref");
+
+// underlying type of enums
+static_assert(std::is_integral<underlying_type<SimpleEnum>::type>::value,
+              "simple enum must have some integral type");
+static_assert(
+    std::is_same<underlying_type<EnumWithExplicitType>::type, uint64_t>::value,
+    "explicit type must be detected");
+static_assert(std::is_same<underlying_type<ScopedEnum>::type, int>::value,
+              "scoped enum defaults to int");
+
 }  // namespace
 }  // namespace base