unnecessary_set_literal
Braces unnecessarily wrap this expression in a set literal.
Description
#The analyzer produces this diagnostic when a function that has a return type of void
, Future<void>
, or FutureOr<void>
uses an expression function body (=>
) and the returned value is a literal set containing a single element.
Although the language allows it, returning a value from a void
function isn't useful because it can't be used at the call site. In this particular case the return is often due to a misunderstanding about the syntax. The braces aren't necessary and can be removed.
Example
#The following code produces this diagnostic because the closure being passed to g
has a return type of void
, but is returning a set:
void f() {
g(() => {1});
}
void g(void Function() p) {}
Common fixes
#Remove the braces from around the value:
void f() {
g(() => 1);
}
void g(void Function() p) {}
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.