prefer_is_not_operator
Use the 'is!' operator rather than negating the value of the 'is' operator.
Description
#The analyzer produces this diagnostic when the prefix !
operator is used to negate the result of an is
test.
Example
#The following code produces this diagnostic because the result of testing to see whether o
is a String
is negated using the prefix !
operator:
dart
String f(Object o) {
if (!(o is String)) {
return o.toString();
}
return o;
}
Common fixes
#Use the is!
operator instead:
dart
String f(Object o) {
if (o is! String) {
return o.toString();
}
return o;
}
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.