equal_elements_in_set

Two elements in a set literal shouldn't be equal.

The analyzer produces this diagnostic when an element in a non-constant set is the same as a previous element in the same set. If two elements are the same, then the second value is ignored, which makes having both elements pointless and likely signals a bug.

The following code produces this diagnostic because the element 1 appears twice:

const a = 1;
const b = 1;
var s = <int>{a, b};

If both elements should be included in the set, then change one of the elements:

const a = 1;
const b = 2;
var s = <int>{a, b};

If only one of the elements is needed, then remove the one that isn't needed:

const a = 1;
var s = <int>{a};

Note that literal sets preserve the order of their elements, so the choice of which element to remove might affect the order in which elements are returned by an iterator.