generic_struct_subclass

The class '{0}' can't extend 'Struct' or 'Union' because '{0}' is generic.

The analyzer produces this diagnostic when a subclass of either Struct or Union has a type parameter.

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

The following code produces this diagnostic because the class S defines the type parameter T:

import 'dart:ffi';

final class S<T> extends Struct {
  external Pointer notEmpty;
}

Remove the type parameters from the class:

import 'dart:ffi';

final class S extends Struct {
  external Pointer 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.