Limits of implicit conversion of class arrays

[Per Nordlöw]

On Thursday, 28 March 2024 at 01:53:52 UTC, Steven Schveighoffer 
wrote:
>> ```d
>> class Base {}
>> class Derived : Base {}
>>
>> @safe pure nothrow unittest {
>> 	Base b;
>> 	Derived d;
>> 	b = d; // pass
>>
>> 	Base[] bs;
>> 	Derived[] ds;
>> 	bs ~= ds; // pass
>> 	bs = ds; // fail [1], should pass
>> 	bs = cast(Base[])ds; // fail [2], should pass
>> }
>> ```
>
> Yes, it's unsafe, as you can replace an element of `ds` with 
> something that has no relation to `Derived`.

This is a suggested change that when _applied_ will make the code 
unsafe yes. But the code in its current form is safe and the 
compiler could be extended to prove it.