C++ contracts are not a compile-time construct, they're a runtime construct.

Take the example from the article. The contract trips at runtime, not at compile time.

The only required enforcement is runtime (even then it is optional). However nothing stops the compiler from detecting a violation at compile and time failing because of an error (or perhaps warning?)

There is a lot of interest in static analysis enforcing contracts, but this will likely require some additions to the contract specification.

	▲	steveklabnik 6 hours ago \| parent [-]
		I mean, what stops it is > this will likely require some additions to the contract specification. You need a lot more machinery to move this stuff to compile time, and not everything can be checked at compile time. The first example in the post would require you to validate that a <= v's len before indexing in order to be evaluated at compile time, for example. (Which of course is a runtime check anyway...)