default_list_constructor

The default 'List' constructor isn't available when null safety is enabled.

The analyzer produces this diagnostic when it finds a use of the default constructor for the class List in code that has opted in to null safety.

Assuming the following code is opted in to null safety, it produces this diagnostic because it uses the default List constructor:

var l = List<int>();

If no initial size is provided, then convert the code to use a list literal:

var l = <int>[];

If an initial size needs to be provided and there is a single reasonable initial value for the elements, then use List.filled:

var l = List.filled(3, 0);

If an initial size needs to be provided but each element needs to be computed, then use List.generate:

var l = List.generate(3, (i) => i);

Unless stated otherwise, the documentation on this site reflects Dart 3.7.3. Page last updated on 2025-05-08. View source or report an issue.