sdk_version_ui_as_code_in_const_context

The if and spread elements weren't supported in constant expressions until version 2.5.0, but this code is required to be able to run on earlier versions.

The analyzer produces this diagnostic when an if or spread element inside a constant contextConstant contextA region of code where the const keyword is implied and everything within that region must be a constant. Learn more is found in code that has an SDK constraint whose lower bound is less than 2.5.0. Using an if or spread element inside a constant contextConstant contextA region of code where the const keyword is implied and everything within that region must be a constant. Learn more 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 2.5.0:

environment:
  sdk: '>=2.4.0 <2.6.0'

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

const a = [1, 2];
const b = [...a];

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: '>=2.5.0 <2.6.0'

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

const a = [1, 2];
const b = [1, 2];

If that isn't possible, change the code so that the element isn't in a constant contextConstant contextA region of code where the const keyword is implied and everything within that region must be a constant. Learn more:

const a = [1, 2];
var b = [...a];