expressionEdge

The Expression that is cast to castType.

Note: While the type will always stay the same (i.e. the castType), we still want to register ourselves as a type observer to the expression. The reason for that is that we want to propagate the assignedTypes of our expression to us and then possibly to other nodes. This way we can still access the original type of expression (e.g., created by a NewExpression), even when it is cast.