How to sort object by int in dart

The package collection use something similar to the following code but I don’t know why it does not work with it integers and double. But It works with string, duration, datetimes.

extension ListExtensionSort<T> on List<T> {
  void sortByDescOrder<K extends Comparable<K>>(K Function(T element) keyOf,
      [int start = 0, int? end]) {
    sort((b, a) => keyOf(a).compareTo(keyOf(b)));
  }
}
void main() {
  List<Person> people = [
    Person('Alice', 30),
    Person('Bob', 25),
    Person('Charlie', 35),
  ];

  (24).compareTo(56);
  // Sort by age in ascending order
  people.sortByDescOrder((person) => person.age); // does not work
  people.sortByDescOrder((person) => person.name); // does work

  // Print sorted list
  people.forEach((person) {
    print('${person.name}: ${person.age}');
  });
}

Couldn’t infer type parameter ‘K’. Tried to infer ‘int’ for ‘K’ which
doesn’t work: Type parameter ‘K’ is declared to extend ‘Comparable’
producing ‘Comparable’. The type ‘int’ was inferred from:
Parameter ‘keyOf’ declared as ‘K Function(Person)’ but argument is
‘int Function(Person)’.

Update:

I found an overly ugly solution

 people.sortByDescOrder((person) {
    num age = person.age;
    return age;
  });

>Solution :

The issue is that neither int nor double directly implement the Comparable interface. They both extend num which indeed impements the Comparable<num> interface.

This means that while it correctly infers the type for K as int it does not adhere to the bounds of Comparable<int>

There is actually an open issue about this here: https://github.com/dart-lang/sdk/issues/43763

To work around the issue you can just provide the generic type yourself:

people.sortByDescOrder<num>((person) => person.age);