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async_for_in_wrong_context

Contents

The async for-in loop can only be used in an async function.

Description

#

The analyzer produces this diagnostic when an async for-in loop is found in a function or method whose body isn't marked as being either async or async*.

Example

#

The following code produces this diagnostic because the body of f isn't marked as being either async or async*, but f contains an async for-in loop:

dart
void f(list) {
  await for (var e in list) {
    print(e);
  }
}

Common fixes

#

If the function should return a Future, then mark the body with async:

dart
Future<void> f(list) async {
  await for (var e in list) {
    print(e);
  }
}

If the function should return a Stream of values, then mark the body with async*:

dart
Stream<void> f(list) async* {
  await for (var e in list) {
    print(e);
  }
}

If the function should be synchronous, then remove the await before the loop:

dart
void f(list) {
  for (var e in list) {
    print(e);
  }
}

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.