packed_annotation

Structs must have at most one 'Packed' annotation.

The analyzer produces this diagnostic when a subclass of Struct has more than one Packed annotation.

For more information about FFI, see C interop using dart:ffi.

The following code produces this diagnostic because the class C, which is a subclass of Struct, has two Packed annotations:

import 'dart:ffi';

@Packed(1)
@Packed(1)
final class C extends Struct {
  external Pointer<Uint8> notEmpty;
}

Remove all but one of the annotations:

import 'dart:ffi';

@Packed(1)
final class C extends Struct {
  external Pointer<Uint8> notEmpty;
}

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.