sdk_version_ui_as_code

The for, if, and spread elements weren't supported until version 2.3.0, but this code is required to be able to run on earlier versions.

The analyzer produces this diagnostic when a for, if, or spread element is found in code that has an SDK constraint whose lower bound is less than 2.3.0. Using a for, if, or spread element wasn't supported 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 2.3.0:

environment:
  sdk: '>=2.2.0 <2.4.0'

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

var digits = [for (int i = 0; i < 10; i++) i];

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

environment:
  sdk: '>=2.3.0 <2.4.0'

If you need to support older versions of the SDK, then rewrite the code to not make use of those elements:

var digits = _initializeDigits();
​
List<int> _initializeDigits() {
  var digits = <int>[];
  for (int i = 0; i < 10; i++) {
    digits.add(i);
  }
  return digits;
}