Experiment flags

The Dart SDK often contains experimental features, which you can try by passing flags to Dart tools.

To use an experiment with Dart SDK command line tools, pass the corresponding flag to the tool.

For example, to enable the experiments super-mixins and no-slow-checks, add those flags to the dart command:

$ dart run --enable-experiment=super-mixins,no-slow-checks bin/main.dart

Or to the flutter command:

$ flutter run --enable-experiment=super-mixins,no-slow-checks

To enable experiments affecting analysis, use the enable-experiment key in the analysis options file. Here's an example of enabling the experiments super-mixins and no-slow-checks in analysis_options.yaml:

analyzer:
  enable-experiment:
    - super-mixins
    - no-slow-checks

To enable experiments related to running or debugging apps in IDEs, edit the launch configuration.

In launch.json under configurations, add a new toolArgs key containing the desired flags. Example:

 "configurations": [
        {
            "name": "Dart",
            "program": "bin/main.dart",
            "request": "launch",
            "type": "dart",
            "toolArgs": [
                "--enable-experiment=super-mixins,no-slow-checks",
            ],
        }
    ]

For more information, consult the documentation for VS Code launch configurations.

Under VMOptions add the desired flags. Example:

<component name="ProjectRunConfigurationManager">
  <configuration default="false" name="Run main" type="DartCommandLineRunConfigurationType" factoryName="Dart Command Line Application">
    <option name="VMOptions" value="--enable-experiment=non-nullable" />
    <option name="filePath" value="$PROJECT_DIR$/bin/main.dart" />
    <method v="2" />
  </configuration>
</component>

For more information, consult the instructions for Android Studio run/debug configurations.

• For a complete list of experiments, see the Dart SDK file experimental_features.yaml.
• For information on procedures and expectations for experiment flags, see the documentation of the process for changes that are behind experimental flags.