field_initializer_in_struct

Constructors in subclasses of 'Struct' and 'Union' can't have field initializers.

The analyzer produces this diagnostic when a constructor in a subclass of either Struct or Union has one or more field initializers.

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

The following code produces this diagnostic because the class C has a constructor with an initializer for the field f:

// @dart = 2.9
import 'dart:ffi';

final class C extends Struct {
  @Int32()
  int f;

  C() : f = 0;
}

Remove the field initializer:

// @dart = 2.9
import 'dart:ffi';

final class C extends Struct {
  @Int32()
  int f;

  C();
}

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.