kwalrath/variance_motivation_solution.dart

## variance_motivation_solution.dart
// Add a contravariant variance modifier
class Writer<in T> {
  void write(T x) => print(x);
}

main() {
  // Error! Cannot assign Writer<int> to Writer<Object> because the type
  // parameter is contravariantly declared.
  Writer<Object> objectWriter = new Writer<int>();
}
	// Add a contravariant variance modifier
	class Writer<in T> {
	void write(T x) => print(x);
	}

	main() {
	// Error! Cannot assign Writer<int> to Writer<Object> because the type
	// parameter is contravariantly declared.
	Writer<Object> objectWriter = new Writer<int>();
	}