public IEnumerable <IIdentifierInfo> KnownIdentifiers()
 {
     if (m_lambdaParameters != null)
     {
         foreach (var lp in m_lambdaParameters)
         {
             yield return(new IdentifierInfo(lp.Name, lp.Name, IdentifierType.LambdaParameter, (TypeReference)lp.Type, lp));
         }
     }
     foreach (var local in m_localVariables)
     {
         if (local.Name != null)
         {
             yield return(local);                        // Only return variables with a name.
         }
     }
     if (m_parent != null)
     {
         foreach (var fromParent in m_parent.KnownIdentifiers())
         {
             yield return(fromParent);
         }
     }
 }