Predicate signature InputSig::localMustFlowStep

Holds if the value of node2 is given by node1.

This predicate is combined with type information in the following way: If the data flow library is able to compute an improved type for node1 then it will also conclude that this type applies to node2. Vice versa, if node2 must be visited along a flow path, then any type known for node2 must also apply to node1.