const_spread_expected_list_or_set

A list or a set is expected in this spread.

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.

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

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

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

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