On Mon, 2 Jun 2025 at 23:44, Tom Honermann <tom_at_[hidden]> wrote:
> It's fairly easy to find WG21 members who think it's absolutely
> necessary to have "more in-source syntax" to decide the difference
> between a contract
> that scales its behavior from full checking to almost-nothing, and a
> contract that scales its behavior from full checking to almost-nothing
> and onwards
> to assumption of the condition stated in the contract.
>
> I assume you are referring to an in-source mechanism to select a contract semantic along the lines of those proposed in P3400 (Controlling Contract-Assertion Properties). If so, I agree.

Funny choice of words, "assume". :D

> My statement regarding not seeing a need for more in-source syntax is based on a perception that [[assume(expr)]], inline functions, and a facility to control the contract semantic (whether in-source or otherwise) suffices to provide the benefits the proposer seeks.

Well,
1) if we make [[assume]] usable on function declarations or in
particular function parameters, we have already arrived at "more
in-source syntax"
2) a semantics selection mechanism can't select something that's not
an available semantic
3) if we make 'assume' such a semantic, there's going to be opposition
to allow it as a possible implementation-chosen semantic for the C++26
contracts syntax
4) and it's likely that even if we end up standardizing an in-source
semantics-selection syntax, there's likely going to be people in WG21
who will want
a syntax that without any possibility of plugging otherwise prevents
choosing an 'assume' semantic, no matter what the mechanism triggered
by the in-source
selection syntax attempts to do.

You may not think such additional syntax is necessary. But there are
people in WG21 who do.

Therefore I would be hesitant to suggest that WG21 has made up its
mind on this matter, and it's a fruitless exercise to entertain "more
in-source syntax" to
enable such assumptions. Some WG21 members are going to insist that
such more-syntax is used for it.