strange behavior of by-value function arguments in postcondition

[bauss]

On Tuesday, 31 August 2021 at 12:45:29 UTC, Andrzej K. wrote:
> On Tuesday, 31 August 2021 at 12:39:59 UTC, bauss wrote:
>> On Tuesday, 31 August 2021 at 12:35:54 UTC, Andrzej K. wrote:
>>>
>>> I guess, the question here is, who are the postconditions 
>>> for? Are they for the caller (to guarantee something that the 
>>> caller understands)? Or are they for the callee (in order to 
>>> automatically inject assertions into function body)? If it is 
>>> the latter, then the current semantics are fine.
>>
>> The postconditions are for the maintainer to ensure the 
>> function actually works as expected.
>>
>> If the asserts don't pass then the function has a bug.
>>
>> Assert statements are never for the user and always for the 
>> maintainer.
>
> Yup. This explanation is compatible with what the compiler does.
>
> What puzzles me now is that if it is for implementer only, why 
> should it be the part of the function signature (as opposed to 
> the function body).

I think it's just because it's better to separate asserts from 
functionality. It makes it much more readable, especially for 
larger functions etc.

It also makes it possible to assert the return value from 
functions with multiple return statements but in a single place.

Otherwise you'd have to do something hacky or use scope 
statements, which ultimately ends up being extra boilerplate.