I’m saying we have decades of experience with macro based systems, which
defines the floor of features/expectations. The consensus is P2900 is
better taken as a whole. There are things i think should be different with
p2900, but p2900 represents consensus. There has been no evidence put
forward that there is a more correct course. Based on those decades of
experience here are no outstanding questions that having a TS would answer.

If i am wrong, please list precise questions that a TS would answer. “We
don’t have enough experience” is a statement.

Cheers,

On Mon, Oct 20, 2025 at 11:54 AM John Spicer <jhs_at_[hidden]> wrote:

> You keep saying things like we have “decades of experience with
> macro-based systems”.
>
> If contracts were remotely similar to macro-based systems, we would not be
> having this discussion.
>
> The problem is that contracts are *vastly* different.
>
> If you put P2900 and macro-based systems in the same set, that means you
> don’t understand one or the other.
>
> John.
>
> On Oct 20, 2025, at 2:22 PM, Ryan McDougall via SG21 <
> sg21_at_[hidden]> wrote:
>
> The "course corrections" do not actually suggest a future course (beyond
> asserting without evidence"we need more experience" and kicking the can
> down the road to a TS) -- we've had years for alternative proposals to be
> put forward, and none have surpassed P2900.
>
> We *do* have decades of experience with macro-based systems, we *do* have
> decades of experience building software at scale (see Software
> Engineering at Google <https://abseil.io/resources/swe-book>), and we
> *do* know who our users are (see P1995 and P3297) -- and while there are
> many variations on contracts, P2900 represents our best consensus
> interpretation of those decades of experience. Not all of these decisions
> were everyone's first choice, but P2900 is the consensus. There is no
> evidence that any other option would improve that.
>
> Multiple papers, like P2900 and P3578 <http://wg21.link/p3578> explain
> exactly who the feature is for, and how and why each of these design
> choices were made. There is no reason to believe the current course is
> incorrect, or that another course would be more correct.
>
> On Mon, Oct 20, 2025 at 4:58 AM Ville Voutilainen via SG21 <
> sg21_at_[hidden]> wrote:
>
>> On Mon, 20 Oct 2025 at 14:34, Timur Doumler via SG15
>> <sg15_at_[hidden]> wrote:
>> > Given the above, it seems to me like opposing C++26 contract assertions
>> because you want that checks are always on / always enforced is kinda like
>> this:
>> >
>> > – Alice: "I want safer roads for pedestrians." (reasonable and good
>> request)
>> > – Bob: "Here's a proposal to fund bike lanes in the city." (reasonable
>> and good proposal roughly in the same area but with a different goal)
>> > – Alice: "But bike lanes don't add more crosswalks or reduce speed
>> limits. So they don't make roads safer for pedestrians. Therefore, we
>> should not build bike lanes."
>> >
>> > Here, Alice is committing a logical fallacy. Just because bike lanes
>> are not useful for Alice, it doesn't mean that they're not useful for Bob,
>> and taking away bike lanes from Bob does nothing to give Alice what she
>> wants.
>>
>> The colorful analogy doesn't include considerations where providing
>> bike lanes for Bob and doing nothing else is not entirely harmless for
>> the pedestrians Alice is focused on.
>>
>> It's also incorrect in its suggestion that bike lanes are not useful
>> for Alice. Nobody has said that P2900 isn't useful. That's why it's
>> included
>> in *every* *single* *one* of the currently active proposals suggesting
>> course corrections.
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