equal_keys_in_const_map

Two keys in a constant map literal can't be equal.

The analyzer produces this diagnostic when a key in a constant map is the same as a previous key in the same map. If two keys are the same, then the second value would overwrite the first value, which makes having both pairs pointless.

The following code produces this diagnostic because the key 1 is used twice:

const map = <int, String>{1: 'a', 2: 'b', 1: 'c', 4: 'd'};

If both entries should be included in the map, then change one of the keys to be different:

const map = <int, String>{1: 'a', 2: 'b', 3: 'c', 4: 'd'};

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

const map = <int, String>{1: 'a', 2: 'b', 4: 'd'};

Note that literal maps preserve the order of their entries, so the choice of which entry to remove might affect the order in which keys and values are returned by an iterator.