dartanalyzer报告“入门”教程中的错误

flutter.io/get-started/codelab 产生以下错误:

$ dartanalyzer lib/main.dart
Analyzing lib/main.dart...
  error • The function 'MyApp' isn't defined at lib/main.dart:3:23 • undefined_function
  error • 'MaterialApp' isn't a function at lib/main.dart:8:12 • invocation_of_non_function
  error • 'Scaffold' isn't a function at lib/main.dart:10:13 • invocation_of_non_function
  error • 'AppBar' isn't a function at lib/main.dart:11:17 • invocation_of_non_function
  error • 'Text' isn't a function at lib/main.dart:12:18 • invocation_of_non_function
  error • 'Center' isn't a function at lib/main.dart:14:15 • invocation_of_non_function
  error • 'Text' isn't a function at lib/main.dart:15:18 • invocation_of_non_function
7 errors found.

$ dartanalyzer --version
dartanalyzer version 1.24.3

如何使分析仪正常运行?