analyzer.go
func NewPlanValue(node Expr) (sqltypes.PlanValue, error) {
	switch node := node.(type) {
	case *SQLVal:
		switch node.Type {
		case ValArg:
			return sqltypes.PlanValue{Key: string(node.Val[1:])}, nil
		case IntVal:
			n, err := sqltypes.NewIntegral(string(node.Val))
			if err != nil {
				return sqltypes.PlanValue{}, fmt.Errorf("%v", err)
			}
			return sqltypes.PlanValue{Value: n}, nil
		case StrVal:
			return sqltypes.PlanValue{Value: sqltypes.MakeTrusted(sqltypes.VarBinary, node.Val)}, nil
		case HexVal:
			v, err := node.HexDecode()
			if err != nil {
				return sqltypes.PlanValue{}, fmt.Errorf("%v", err)
			}
			return sqltypes.PlanValue{Value: sqltypes.MakeTrusted(sqltypes.VarBinary, v)}, nil
		}
	case ListArg:
		return sqltypes.PlanValue{ListKey: string(node[2:])}, nil
	case ValTuple:
		pv := sqltypes.PlanValue{
			Values: make([]sqltypes.PlanValue, 0, len(node)),
		}
		for _, val := range node {
			innerpv, err := NewPlanValue(val)
			if err != nil {
				return sqltypes.PlanValue{}, err
			}
			if innerpv.ListKey != "" || innerpv.Values != nil {
				return sqltypes.PlanValue{}, errors.New("unsupported: nested lists")
			}
			pv.Values = append(pv.Values, innerpv)
		}
		return pv, nil
	case *NullVal:
		return sqltypes.PlanValue{}, nil
	}
	return sqltypes.PlanValue{}, fmt.Errorf("expression is too complex '%v'", String(node))
}
func NewPlanValue(node Expr) (sqltypes.PlanValue, error) {
	switch node := node.(type) {
	case *SQLVal:
		switch node.Type {
		case ValArg:
			return sqltypes.PlanValue{Key: string(node.Val[1:])}, nil
		case IntVal:
			n, err := sqltypes.NewIntegral(string(node.Val))
			if err != nil {
				return sqltypes.PlanValue{}, fmt.Errorf("%v", err)
			}
			return sqltypes.PlanValue{Value: n}, nil
		case StrVal:
			return sqltypes.PlanValue{Value: sqltypes.MakeTrusted(sqltypes.VarBinary, node.Val)}, nil
		case HexVal:
			v, err := node.HexDecode()
			if err != nil {
				return sqltypes.PlanValue{}, fmt.Errorf("%v", err)
			}
			return sqltypes.PlanValue{Value: sqltypes.MakeTrusted(sqltypes.VarBinary, v)}, nil
		}
	case ListArg:
		return sqltypes.PlanValue{ListKey: string(node[2:])}, nil
	case ValTuple:
		pv := sqltypes.PlanValue{
			Values: make([]sqltypes.PlanValue, 0, len(node)),
		}
		for _, val := range node {
			innerpv, err := NewPlanValue(val)
			if err != nil {
				return sqltypes.PlanValue{}, err
			}
			if innerpv.ListKey != "" || innerpv.Values != nil {
				return sqltypes.PlanValue{}, errors.New("unsupported: nested lists")
			}
			pv.Values = append(pv.Values, innerpv)
		}
		return pv, nil
	case *NullVal:
		return sqltypes.PlanValue{}, nil
	}
	return sqltypes.PlanValue{}, fmt.Errorf("expression is too complex '%v'", String(node))
}
// NewPlanValue builds a sqltypes.PlanValue from an Expr.