Set the default operator >> to not compile unless there is a scalar...

Set the default operator >> to not compile unless there is a scalar conversion, so it doesn't interfere with user-defined types

include/yaml-cpp/old-api/conversion.h

@@ -14,6 +14,17 @@
 
 namespace YAML
 {
+	// traits for conversion
+	
+	template<typename T>
+	struct is_scalar_convertible { enum { value = is_numeric<T>::value }; };
+	
+	template<> struct is_scalar_convertible<std::string> { enum { value = true }; };
+	template<> struct is_scalar_convertible<bool> { enum { value = true }; };
+	template<> struct is_scalar_convertible<_Null> { enum { value = true }; };
+
+	// actual conversion
+	
 	inline bool Convert(const std::string& input, std::string& output) {
 		output = input;
 		return true;

include/yaml-cpp/old-api/node.h

@@ -66,7 +66,7 @@ namespace YAML
 		const T to() const;
 
 		template <typename T>
-		friend YAML_CPP_API void operator >> (const Node& node, T& value);
+		friend YAML_CPP_API typename enable_if<is_scalar_convertible<T> >::type operator >> (const Node& node, T& value);
 
 		// retrieval for maps and sequences
 		template <typename T>

include/yaml-cpp/old-api/nodeimpl.h

@@ -20,7 +20,7 @@ namespace YAML
 	}
 
 	template <typename T>
-	inline void operator >> (const Node& node, T& value) {
+	inline typename enable_if<is_scalar_convertible<T> >::type operator >> (const Node& node, T& value) {
 		if(!ConvertScalar(node, value))
 			throw InvalidScalar(node.m_mark);
 	}