# const_spread_expected_list_or_set

> Details about the const_spread_expected_list_or_set diagnostic produced by the Dart analyzer.



_A list or a set is expected in this spread._

## Description

The analyzer produces this diagnostic when the expression of a spread
operator in a constant list or set evaluates to something other than a list
or a set.

## Example

The following code produces this diagnostic because the value of `list1` is
`null`, which is neither a list nor a set:

```dart
const dynamic list1 = 42;
const List<int> list2 = [...[!list1!]];
```

## Common fixes

Change the expression to something that evaluates to either a constant list
or a constant set:

```dart
const dynamic list1 = [42];
const List<int> list2 = [...list1];
```

