case_expression_type_implements_equals
The switch case expression type '{0}' can't override the '==' operator.
Description
#The analyzer produces this diagnostic when the type of the expression following the keyword case
has an implementation of the ==
operator other than the one in Object
.
Example
#The following code produces this diagnostic because the expression following the keyword case
(C(0)
) has the type C
, and the class C
overrides the ==
operator:
class C {
final int value;
const C(this.value);
bool operator ==(Object other) {
return false;
}
}
void f(C c) {
switch (c) {
case C(0):
break;
}
}
Common fixes
#If there isn't a strong reason not to do so, then rewrite the code to use an if-else structure:
class C {
final int value;
const C(this.value);
bool operator ==(Object other) {
return false;
}
}
void f(C c) {
if (c == C(0)) {
// ...
}
}
If you can't rewrite the switch statement and the implementation of ==
isn't necessary, then remove it:
class C {
final int value;
const C(this.value);
}
void f(C c) {
switch (c) {
case C(0):
break;
}
}
If you can't rewrite the switch statement and you can't remove the definition of ==
, then find some other value that can be used to control the switch:
class C {
final int value;
const C(this.value);
bool operator ==(Object other) {
return false;
}
}
void f(C c) {
switch (c.value) {
case 0:
break;
}
}
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.