The chosen answer is no longer valid when you try overloads using the == operator in the new version. Now you need to do this:

class MyClass {
  @override
  bool operator ==(other) {
    // compare this to other
  }
}

But it’s not safe. other is not specified as a type, Something unexpected may happened. For example:

void main() {
  var a = A(1);
  var b = B(1);
  var result = a == b;
  print(result); //result is true
}

class A {
  A(this.index);

  final int index;

  @override
  bool operator ==(other) => other.index == index;
}

class B {
  B(this.index);

  final int index;
}

So you could do like this:

class A {
  A(this.index);

  final int index;

  @override
  bool operator ==(covariant A other) => other.index == index;
}

You need to use covariant. Because Object overloads the == operator.

or you can

Test Object Type:
visit: hash_and_equals

class A {
  A(this.index);

  final int index;

  @override
  bool operator ==(other) => other is A && (other.index == index);

  @override
  int get hashCode => index;
}