Why aren't generic type constraints inheritable/hierarchically enforced

Question

Item class

public class Item
{
    public bool Check(int value) { ... }
}

Base abstract class with generic type constraint

Answer 1

I think you're confused becuase you're declaring you derived class with TItem as well.

If you think about it if you were using Q instead so.

public class MyClass : BaseClass
{
 ...
}

Then how is it to be determined that Q is of the type item?

You need to add the constraint to the derived classes Generic Type as well so

public class MyClass : BaseClass were Q : Item { ... }