Previously, expressions such as SubQueryExpression, QuerySourceReferenceExpression, and ExtensionExpression all used non-unique default values for their NodeType property.
This has now changed. re-linq now reserves ExpressionType values from 100000 to 150000 for its own expressions. Custom LINQ providers can use 150001 and above.
Subclasses of ExtensionExpression can decide whether to use the default value of 150000 or a custom one by choosing the appropriate constructor.
This change was needed in order to enable re-linq users to apply light-weight transformations using IExpressionTransformer<T> to re-linq-specific expressions.