`restricted` member variables

[Ola Fosheim Grøstad]

On Tuesday, 21 June 2022 at 01:20:27 UTC, Mike Parker wrote:
> Targeted invariants would be nice. Not a must have, probably a 
> niche case, but definitely nice to have.

The intent is to give the compiler a constraint, so the 
assumption that the compiler doesn’t have access to the full 
constraint is the same as assuming that the programmer doesn’t 
know what he is doing. The right thing to do is to help the 
programmer and reject such illdpecified constraints.

If you specify preconditions/postconditions then the exit check 
should be considered part of the assumed precondition and the 
asserted postcondition. If you allow the class invariant  to be 
hidden from the compiler then you mess up the preconditions.

Asserts only add information that is redundant and would be 
removed by a perfect static analysis. If that isn’t possible then 
either the invariant/assert is badly written or the program is 
wrong.