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 3.9.2. Page last updated on 2025-9-1. View source or report an issue.