interface function member declarations needing parameter attributes ?

[Adam D Ruppe]

On Saturday, 17 July 2021 at 22:43:15 UTC, someone wrote:
> So the lesson learned is that interfaces can also mandate 
> member function's parameter attributes then ... right ?

A subclass must accept anything the parent class can, but it can 
also make it stricter if you want.

class Base {
         void foo(Object o) {}
}

class Derived : Base {
         override void foo(const Object o) {}
}


That's legal because const also accepts mutable. Derived is 
stricter than Base which is permitted. But the other way around:

class Base {
         void foo(const Object o) {}
}

class Derived : Base {
         override void foo(Object o) {}
}

is NOT allowed because the mutable thing in derived cannot be 
passed back to the base interface implicitly.