CoCtrlStruct constructor
Constructor. Optional counter, end, and iter
parameters for different types of control structures.
For example, a for-loop would have a counter but
a while loop would have a condition stored in node.
Implementation
CoCtrlStruct(this.node, {num? counter, num? end, int? stmtIdx, this.iter})
: counter = counter ?? 0,
end = end ?? 0,
stmtIdx = stmtIdx ?? 0;