invalid_null_aware_operator
The element can't be null, so the null-aware operator '?' is unnecessary.
The map entry key can't be null, so the null-aware operator '?' is unnecessary.
The map entry value can't be null, so the null-aware operator '?' is unnecessary.
The receiver can't be 'null' because of short-circuiting, so the null-aware operator '{0}' can't be used.
The receiver can't be null, so the null-aware operator '{0}' is unnecessary.
Description
#The analyzer produces this diagnostic when a null-aware operator (?.
, ?..
, ?[
, ?..[
, or ...?
) is used on a receiver that's known to be non-nullable.
Examples
#The following code produces this diagnostic because s
can't be null
:
int? getLength(String s) {
return s?.length;
}
The following code produces this diagnostic because a
can't be null
:
var a = [];
var b = [...?a];
The following code produces this diagnostic because s?.length
can't return null
:
void f(String? s) {
s?.length?.isEven;
}
The reason s?.length
can't return null
is because the null-aware operator following s
short-circuits the evaluation of both length
and isEven
if s
is null
. In other words, if s
is null
, then neither length
nor isEven
will be invoked, and if s
is non-null
, then length
can't return a null
value. Either way, isEven
can't be invoked on a null
value, so the null-aware operator isn't necessary. See Understanding null safety for more details.
The following code produces this diagnostic because s
can't be null
.
void f(Object? o) {
var s = o as String;
s?.length;
}
The reason s
can't be null, despite the fact that o
can be null
, is because of the cast to String
, which is a non-nullable type. If o
ever has the value null
, the cast will fail and the invocation of length
will not happen.
The following code produces this diagnostic because s
can't be null
:
List<String> makeSingletonList(String s) {
return <String>[?s];
}
Common fixes
#Replace the null-aware operator with a non-null-aware equivalent; for example, change ?.
to .
:
int getLength(String s) {
return s.length;
}
(Note that the return type was also changed to be non-nullable, which might not be appropriate in some cases.)
Unless stated otherwise, the documentation on this site reflects Dart 3.7.3. Page last updated on 2025-05-08. View source or report an issue.