unnecessary_null_in_if_null_operators

Unnecessary use of '??' with 'null'.

The analyzer produces this diagnostic when the right operand of the ?? operator is the literal null.

The following code produces this diagnostic because the right-hand operand of the ?? operator is null:

String? f(String? s) => s ?? null;

If a non-null value should be used for the right-hand operand, then change the right-hand side:

String f(String? s) => s ?? '';

If there is no non-null value to use for the right-hand operand, then remove the operator and the right-hand operand:

String? f(String? s) => s;