dead_ code_ on_ catch_ subtype
Dead code: This on-catch block won't be executed because '{0}' is a subtype of '{1}' and hence will have been caught already.
Description
#
The analyzer produces this diagnostic when a
catch
clause is found that
can't be executed because it is after a
catch
clause that catches either
the same type or a supertype of the clause's type. The first
catch
clause
that matches the thrown object is selected, and the earlier clause always
matches anything matchable by the highlighted clause, so the highlighted
clause will never be selected.
Example
#The following code produces this diagnostic:
void f() {
try {
} on num {
} on int {
}
}
Common fixes
#If the clause should be selectable, then move the clause before the general clause:
void f() {
try {
} on int {
} on num {
}
}
If the clause doesn't need to be selectable, then remove it:
void f() {
try {
} on num {
}
}
Unless stated otherwise, the documentation on this site reflects Dart 3.9.2. Page last updated on 2025-9-4. View source or report an issue.