alt Hacker NewsThe issue is that contracts are less flexible than the existing capabilities in practice, it is limited syntactic sugar.
Contracts were sold with the idea of aiding compile-time verification, a noble purpose. The combination of concepts + constexpr allows you to do deeper compile-time verification today by other means than contracts can check. It isn’t obvious that this will ever not be the case. This means contracts is relegated to being another flavor of C asserts.
C++26 contracts are arguably unnecessary because we can achieve the same results other ways, sometimes with stronger properties. I’m a proponent of features that clean up the syntax but C++ contracts look like a nod to people that still use legacy C asserts. That’s fine but it also perpetuates an inadequate model of what assertions should be capable of expressing.
People figured out how to do with C++20 better than what contracts promised.
There's nothing "legacy" about checking invariants at runtime, and you can't simultaneously dismiss the concerns of people doing so on the grounds that they're "still us[ing] legacy C asserts" when you deny them an alternative to "legacy C asserts". That's question-begging.
> People figured out how to do with C++20 better than what contracts promised.
What contracts used to promise is irrelevant. The contracts on the table modernized runtime assertions and are irrelevant to concepts, constexpr, and related facilities.
Is the contracts feature more useful than C's assert()?
If you want to argue that we're better off with the old macro, do so directly. Concepts, in this context, amount to irrelevant distraction.