尽管使用 Dart 2.0，但不能省略 'new' 关键字

Question

当我运行测试我的应用程序时，我得到这个异常：

NoSuchMethodError: Attempted to use type 'SimplePipe' as a function. Since types do not define a method 'call', this is not possible. Did you intend to call the SimplePipe constructor and forget the 'new' operator?

我从这个错误消息中得出结论，我的项目实际上没有使用 Dart 2.0，而是 Dart 1.0。不过，SDK 在 pubspec.yaml 中设置为 >=2.0.0-dev.53.0 <2.0.0。

我的一个朋友在他的 PC 上运行在相同条件下进行相同测试时收到此错误消息。他已经尝试运行ning pub get.

Dart 2.0.0-dev.54.0.flutter-46ab040e58 is incompatible with your dependencies' SDK constraints. Please run "pub get" again

pubspec.yaml:

name: timecoder_common
description: A Dart Libary containin all the shared logic
version: 0.0.1

environment:
  sdk: '>=2.0.0-dev.53.0 <2.0.0'

dependencies:
  uuid: "^0.5.3"
  json_annotation: "^0.2.3"
  http: "^0.11.3"
  rxdart: "^0.16.6"
  test: "^0.12.34"

dev_dependencies:
  build_runner: "^0.8.0"
  json_serializable: "^0.5.0"

Answer 1

Dart 2.0 SDK 默认不启用此功能（目前）。

对于 Flutter，您将 need to be on the latest SDK:

In this blog post, we’ll take a deeper look at the specific improvements we’ve made in Beta 3 itself.

对于命令行 VM，如评论中所述，您必须选择加入：

dart --preview-dart-2 bin/main.dart

尽管使用 Dart 2.0，但不能省略 'new' 关键字

Cannot omit 'new' keyword despite using Dart 2.0

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