compound_implements_finalizable

The class '{0}' can't implement Finalizable.

The analyzer produces this diagnostic when a subclass of either Struct or Union implements Finalizable.

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

The following code produces this diagnostic because the class S implements Finalizable:

import 'dart:ffi';

final class S extends Struct implements Finalizable {
  external Pointer notEmpty;
}

Try removing the implements clause from the class:

import 'dart:ffi';

final class S extends Struct {
  external Pointer notEmpty;
}