Clone of unsubmitted cr/176529515. Introduce parameterless expectations.

googlemock/include/gmock/internal/gmock-internal-utils.h

@@ -344,6 +344,21 @@ GTEST_API_ bool LogIsVisible(LogSeverity severity);
 GTEST_API_ void Log(LogSeverity severity, const std::string& message,
                     int stack_frames_to_skip);
 
+// A marker class that is used to resolve parameterless expectations to the
+// correct overload. This must not be instantiable, to prevent client code from
+// accidentally resolving to the overload; for example:
+//
+//    ON_CALL(mock, Method({}, nullptr))…
+//
+class WithoutMatchers {
+ private:
+  WithoutMatchers() {}
+  friend WithoutMatchers GetWithoutMatchers();
+};
+
+// Internal use only: access the singleton instance of WithoutMatchers.
+WithoutMatchers GetWithoutMatchers();
+
 // TODO(wan@google.com): group all type utilities together.
 
 // Type traits.