code: function Trace(input, pos1, pos2, expr, succeeded, bindings, optChildren) {
    this.input = input;
    this.pos = this.pos1 = pos1;
    this.pos2 = pos2;
    this.source = new Interval(input, pos1, pos2);
    this.expr = expr;
    this.bindings = bindings;
    this.children = optChildren || [];
    this.terminatingLREntry = null;
  
    this._flags = succeeded ? Flags.succeeded : 0;
  }
docs: ----------------- Trace -----------------