Flutter Hive构建Adapter报错：需先修复Dart代码语法问题

我是编程新手，英语是第二语言。跟着讲师在IDE终端执行Flutter Hive构建命令生成Adapter类，步骤如下：

• 先执行 flutter packages pub run build_runner build
• 若失败则执行 flutter pub get && flutter pub run build_runner build --delete-conflicting-outputs web

但执行后报错，终端提示构建器要求Dart代码无语法错误，bank_account.dart文件第8行第3列必须提供函数体，具体错误信息如下：

E:\android\meter_switch>flutter packages pub run build_runner build

[INFO] Generating build script...
[INFO] Generating build script completed, took 711ms

[INFO] Initializing inputs
[INFO] Reading cached asset graph...
[INFO] Reading cached asset graph completed, took 124ms

[INFO] Checking for updates since last build...
[INFO] Checking for updates since last build completed, took 1.1s

[INFO] Running build...
[SEVERE] hive_generator:hive_generator on lib/bank_account.dart:

This builder requires Dart inputs without syntax errors.
However, package:meter_switch/bank_account.dart (or an existing part) contains the following errors.
bank_account.dart:8:3: A function body must be provided.

Try fixing the errors and re-running the build.

[INFO] Running build completed, took 1.4s

[INFO] Caching finalized dependency graph...
[INFO] Caching finalized dependency graph completed, took 91ms

[SEVERE] Failed after 1.5s
pub finished with exit code 1

相关截图说明：

1. 执行命令前的代码状态截图
2. 代码报错位置截图
3. 执行命令后的代码状态截图

内容的提问来源于stack exchange，提问作者Saad Mansoor