Mojo C++ bindings: more consistent Clone() and Equals().

mojo/public/cpp/bindings/lib/template_util.h

Index: mojo/public/cpp/bindings/lib/template_util.h
diff --git a/mojo/public/cpp/bindings/lib/template_util.h b/mojo/public/cpp/bindings/lib/template_util.h
index cca06de0a10cd17ee79089d0c687097db2020905..34011cf4b90b10068b6ceb6f723c5c9ed0ba77bd 100644
--- a/mojo/public/cpp/bindings/lib/template_util.h
+++ b/mojo/public/cpp/bindings/lib/template_util.h
@@ -5,6 +5,8 @@
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_TEMPLATE_UTIL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_TEMPLATE_UTIL_H_
 
+#include <type_traits>
+
 namespace mojo {
 namespace internal {
 
@@ -118,6 +120,54 @@ struct Conditional<false, T, F> {
   typedef F type;
 };
 
+template <typename T>
+struct HasCloneMethod {
+  template <typename U>
+  static char Test(decltype(&U::Clone));
+  template <typename U>
+  static int Test(...);
+  static const bool value = sizeof(Test<T>(0)) == sizeof(char);
+
+ private:
+  EnsureTypeIsComplete<T> check_t_;
+};
+
+template <typename T,
+          typename std::enable_if<HasCloneMethod<T>::value>::type* = nullptr>
+T Clone(const T& input) {
+  return input.Clone();
+};
+
+template <typename T,
+          typename std::enable_if<!HasCloneMethod<T>::value>::type* = nullptr>
+T Clone(const T& input) {
+  return input;
+}
+
+template <typename T>
+struct HasEqualsMethod {
+  template <typename U>
+  static char Test(decltype(&U::Equals));
+  template <typename U>
+  static int Test(...);
+  static const bool value = sizeof(Test<T>(0)) == sizeof(char);
+
+ private:
+  EnsureTypeIsComplete<T> check_t_;
+};
+
+template <typename T,
+          typename std::enable_if<HasEqualsMethod<T>::value>::type* = nullptr>
+bool Equals(const T& a, const T& b) {
+  return a.Equals(b);
+};
+
+template <typename T,
+          typename std::enable_if<!HasEqualsMethod<T>::value>::type* = nullptr>
+bool Equals(const T& a, const T& b) {
+  return a == b;
+}
+
 }  // namespace internal
 }  // namespace mojo