On Wednesday, 19 March 2025 11:56:23 Pacific Daylight Time Sebastian Wittmeier
via Std-Proposals wrote:
> That is probably the best explanation.
>
> So we would potentially have 3 declarations/definitions:
>
> - An [unimplemented] declaration
>
> - An actual declaration

Why do you have both declarations in the first place? Why can't you just edit
the first one and drop the =delete("Unimplemented") portion?

I see no reason why two separate projects would be trying to complement
themselves this way. It would be fragile: what happens if the include order
changes somehow and the second definition isn't available? Why is the third
codebase that needs this function even including the first? And what happens if
the first one suddenly starts providing the functionality, will the compilation
break because of double definition of the function?

The more likely condition is that the second project implementing the
functionality provides it with a different function name, which the third code
uses, and we ignore the =delete'd declaration as irrelevant.

> - A definition (possibly in another TU)
>
> In the status quo, if the actual declaration and the definition is combined,
> the error would appear in the link stage. But the error should be earlier.
>
> In the status quo, if the unimplemented declaration would delete instead,
> this decision could not be overridden, e.g. in another included header.

I'm questioning this motivation: how can you be sure of reliably overriding a
declaration in a situation where simply modifying the declaration isn't
possible?

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Principal Engineer - Intel DCAI Platform & System Engineering