generic_ struct_ subclass
The class '{0}' can't extend 'Struct' or 'Union' because '{0}' is generic.
Description
#
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.
Example
#
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;
}
Common fixes
#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 3.9.2. Page last updated on 2025-9-1. View source or report an issue.