The column type `DECIMAL(20,0)` is restored incorrectly as `DECIMAL`

[kennytm]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

package main

import (
	"fmt"
	"github.com/pingcap/parser"
	"github.com/pingcap/parser/format"
	_ "github.com/pingcap/tidb/types/parser_driver"
	"strings"
)

func main() {
	p := parser.New()
	nodes, _ := p.ParseOneStmt(`
		create table precise_types (
			c DECIMAL(20,0) NOT NULL,
			d DOUBLE(20,0) NOT NULL
		);
	`, "", "")

	var s strings.Builder
	ctx := format.NewRestoreCtx(format.DefaultRestoreFlags, &s)
	nodes.Restore(ctx)

	fmt.Println(s.String())
}

2. What did you expect to see?

Prints

CREATE TABLE `precise_types` (`c` DECIMAL(20) NOT NULL,`d` DOUBLE(20,0) NOT NULL)

3. What did you see instead?

The precision is just directly omitted.

CREATE TABLE `precise_types` (`c` DECIMAL NOT NULL,`d` DOUBLE NOT NULL)

4. What version of TiDB SQL Parser are you using?

master (366172d)