title: How to fix "Failed to snapshot build script"
body: <p>I installed flutter for web and dart sdk. Added to path bin folders. Ran <code>flutter pub global activate webdev</code> and <code>flutter pub upgrade</code>, but after entering <code>webdev serve</code> I always getting error": </p>
  
  <pre><code>[SEVERE] Failed to snapshot build script .dart_tool/build/entrypoint/build.dart.
  [SEVERE] This is likely caused by a misconfigured builder definition.
  [SEVERE] /C:/flutter/.pub-cache/hosted/pub.dartlang.org/protobuf-0.13.16/lib/src/protobuf/builder_info.dart:43:34: Error: Method not found: 'MapFieldInfo.map'.    _addField(MapFieldInfo&lt;K, V&gt;.map(name, tagNumber, index, PbFieldType.M,                                 ^^^/C:/flutter/.pub-cache/hosted/pub.dartlang.org/protobuf-0.13.16/lib/src/protobuf/field_info.dart:45:9: Error: '_mapEntryBuilderInfo' isn't an instance field of this class.        _mapEntryBuilderInfo = null {        ^^^^^^^^^^^^^^^^^^^^/C:/flutter/.pub-cache/hosted/pub.dartlang.org/protobuf-0.13.16/lib/src/protobuf/field_info.dart:61:9: Error: '_mapEntryBuilderInfo' isn't an instance field of this class.        _mapEntryBuilderInfo = null;        ^^^^^^^^^^^^^^^^^^^^/C:/flutter/.pub-cache/hosted/pub.dartlang.org/protobuf-0.13.16/lib/src/protobuf/field_info.dart:68:9: Error: '_mapEntryBuilderInfo' isn't an instance field of this class.        _mapEntryBuilderInfo = null {        ^^^^^^^^^^^^^^^^^^^^/C:/flutter/.pub-cache/hosted/pub.dartlang.org/protobuf-0.13.16/lib/src/protobuf/field_info.dart:82:12: Error: '_mapEntryBuilderInfo' isn't an instance field of this class.      this._mapEntryBuilderInfo])           ^^^^^^^^^^^^^^^^^^^^/C:/flutter/.pub-cache/hosted/pub.dartlang.org/protobuf-0.13.16/lib/src/protobuf/field_info.dart:199:9: Error: Superclass has no constructor named 'FieldInfo._'.      : super._(        ^^^^^/C:/flutter/.pub-cache/hosted/pub.dartlang.org/protobuf-0.13.16/lib/src/protobuf/field_info.dart:195:21: Error: Final field '_mapEntryBuilderInfo' is not initialized.Try to#7      _CommandRunner.runCommand (package:webdev/src/webdev_command_runner.dart:38:24)
  &lt;asynchronous suspension&gt;
  #8      CommandRunner.run.&lt;anonymous closure&gt; (package:args/command_runner.dart:112:25)
  #9      new Future.sync (dart:async/future.dart:224:31)
  #10     CommandRunner.run (package:args/command_runner.dart:112:14)
  #11     run (package:webdev/src/webdev_command_runner.dart:19:56)
  #12     main (file:///C:/flutter/.pub-cache/hosted/pub.dartlang.org/webdev-2.5.1/bin/webdev.dart:17:22)
  &lt;asynchronous suspension&gt;
  #13     _startIsolate.&lt;anonymous closure&gt; (dart:isolate-patch/isolate_patch.dart:303:32)
  #14     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:172:12)
  </code></pre>
  
  <p>flutter doctor: </p>
  
  <pre><code>Doctor summary (to see all details, run flutter doctor -v):
  [√] Flutter (Channel stable, v1.9.1+hotfix.2, on Microsoft Windows [Version 10.0.18362.356], locale ru-RU)
  [X] Android toolchain - develop for Android devices
      X Unable to locate Android SDK.
        Install Android Studio from: https://developer.android.com/studio/index.html
        On first launch it will assist you in installing the Android SDK components.
        (or visit https://flutter.dev/setup/#android-setup for detailed instructions).
        If the Android SDK has been installed to a custom location, set ANDROID_HOME to that location.
        You may also want to add it to your PATH environment variable.
  
  [!] Android Studio (not installed)
  [√] VS Code (version 1.38.1)
  [!] Connected device
      ! No devices available
  
  ! Doctor found issues in 3 categories.
  </code></pre>
  
  <p>pubspec.yaml:</p>
  
  <pre><code>name: addd
  description: An app built using Flutter for web
  
  environment:
    # You must be using Flutter &gt;=1.5.0 or Dart &gt;=2.3.0
    sdk: '&gt;=2.3.0 &lt;3.0.0'
  
  dependencies:
    flutter_web: any
    flutter_web_ui: any
  
  dev_dependencies:
    build_runner: ^1.5.0
    build_web_compilers: ^2.1.0
    pedantic: ^1.7.0
  
  dependency_overrides:
    flutter_web:
      git:
        url: https://github.com/flutter/flutter_web
        path: packages/flutter_web
    flutter_web_ui:
      git:
        url: https://github.com/flutter/flutter_web
        path: packages/flutter_web_ui
  </code></pre>
  
  <p>How fix that?</p>
  
  <p>UPD. Added some more detailts (flutter doctor and pubspec.yaml)</p>