An Example of Const Factories in Dart

const_factories.dart

// `const factory` basically only redirects the construction of the object.
// A `const` redirecting constructor must redirect to a `const` constructor.

main() {
  const A a1 = A('hello');
  print(a1);
  const A a2 = A.redirected2('hello');
  print(a2);
  
  final A a3 = A('hello');
  A a4 = A('hello');
  
  print(identical(a1, a2)); // true
  print(identical(a1, a3)); // false
  print(identical(a1, a4)); // false
}

class A {
  final String testField;
  
  const factory A.redirected(String testField) = A;
  
  const factory A.redirected2(String testField) = A._;
  
  const A(this.testField); // should be `const`
  
  const A._(this.testField); // should be `const`
  
  String toString() => this.testField;
}