"A complement assignment operation.
 Right-associative. Any expression may appear on the right-hand side, regardless of precedence.
     people ~= kids
     elements ~= otherElements"
see (`class ComplementOperation`)
shared class ComplementAssignmentOperation(target, other)
        extends SetAssignmentOperation() {
    "The target expression and left operand."
    shared ThenElseExpression target;
    "The right operand."
    shared Expression other;
    "The target expression and left operand."
    see (`value target`)
    shared actual ThenElseExpression leftOperand = target;
    "The right operand."
    see (`value other`)
    shared actual Expression rightOperand = other;
    shared actual [ThenElseExpression, Expression] children = [leftOperand, rightOperand];
    operator = "~=";
    shared actual Result transform<out Result>(Transformer<Result> transformer)
            => transformer.transformComplementAssignmentOperation(this);
    shared actual void visit(Visitor visitor)
            => visitor.visitComplementAssignmentOperation(this);
    shared actual Boolean equals(Object that) {
        if (is ComplementAssignmentOperation that) {
            return leftOperand==that.leftOperand && rightOperand==that.rightOperand;
        } else {
            return false;
    shared actual Integer hash
            => 31 * (leftOperand.hash + 31*rightOperand.hash);
    shared ComplementAssignmentOperation copy(ThenElseExpression leftOperand = this.leftOperand, Expression rightOperand = this.rightOperand) {
        value ret = ComplementAssignmentOperation(leftOperand, rightOperand);
        return ret;