sdk_version_never

The type 'Never' wasn't supported until version 2.12.0, but this code is required to be able to run on earlier versions.

The analyzer produces this diagnostic when a reference to the class Never is found in code that has an SDK constraint whose lower bound is less than 2.12.0. This class wasn't defined in earlier versions, so this code won't be able to run against earlier versions of the SDK.

Here's an example of a pubspec that defines an SDK constraint with a lower bound of less than 2.12.0:

environment:
  sdk: '>=2.5.0 <2.6.0'

In the package that has that pubspec, code like the following produces this diagnostic:

Never n;

If you don't need to support older versions of the SDK, then you can increase the SDK constraint to allow the type to be used:

environment:
  sdk: '>=2.12.0 <2.13.0'

If you need to support older versions of the SDK, then rewrite the code to not reference this class:

dynamic x;

Unless stated otherwise, the documentation on this site reflects Dart 3.8.0. Page last updated on 2025-05-08. View source or report an issue.