--- type.go	2014-06-18 18:26:26.000000000 -0600
+++ /tmp/type.go	2014-09-19 11:51:58.000000000 -0600
@@ -807,13 +807,15 @@
 	concreteTypeToName[ut.base] = name
 }
 
-// Register records a type, identified by a value for that type, under its
-// internal type name.  That name will identify the concrete type of a value
-// sent or received as an interface variable.  Only types that will be
-// transferred as implementations of interface values need to be registered.
-// Expecting to be used only during initialization, it panics if the mapping
-// between types and names is not a bijection.
-func Register(value interface{}) {
+// IsRegisteredName returns true if the given name has already been registered.
+func IsRegisteredName(name string) bool {
+	registerLock.Lock()
+	defer registerLock.Unlock()
+	_, ok := nameToConcreteType[name]
+	return ok
+}
+
+func internalName(value interface{}) string {
 	// Default to printed representation for unnamed types
 	rt := reflect.TypeOf(value)
 	name := rt.String()
@@ -851,7 +853,22 @@
 		}
 	}
 
-	RegisterName(name, value)
+	return name
+}
+
+// Register records a type, identified by a value for that type, under its
+// internal type name.  That name will identify the concrete type of a value
+// sent or received as an interface variable.  Only types that will be
+// transferred as implementations of interface values need to be registered.
+// Expecting to be used only during initialization, it panics if the mapping
+// between types and names is not a bijection.
+func Register(value interface{}) {
+	RegisterName(internalName(value), value)
+}
+
+// IsRegistered returns true if a given type has already been registered.
+func IsRegistered(value interface{}) bool {
+	return IsRegisteredName(internalName(value))
 }
 
 func registerBasics() {