copy must be const?!?

[Dom DiSc]

On Thursday, 25 July 2024 at 22:22:19 UTC, Quirin Schroll wrote:
> On Thursday, 25 July 2024 at 13:07:03 UTC, Jonathan M Davis 
> wrote:
>> But either way, it would cause quite a few problems if IFTI 
>> started instantiating templates in general with mutable 
>> instead of the actual type that it's given, because it's 
>> extremely common that const and immutable types cannot be 
>> converted to mutable.
>
> It’s wild how C++ and D disagree on this one. In C++, a copy 
> constructor must produce a mutable copy. Now, C++ and D 
> disagree on what `const` means and therefore what counts as a 
> mutable copy. But, and this is the key takeaway, C++ never 
> infers `const` on a copy. Never. It does infer `const` on a 
> reference, of course.

sigh.
One more point where C++ made better decisions.

> Nothing of this is out of reach for D. A type for which const 
> objects can’t be copied to initialize a mutable one simply 
> isn’t copyable and therefore can’t be passed by value. A type 
> for which const rvalues can’t be used to initialize a mutable 
> variable aren’t movable.

+1

> However, copying a type [with const] for which there’s a copy 
> constructor that can give you a mutable object is a no-no.

That's my point.