Re: Implementing Rust's borrow checked pointers

[Simon Wright <simon@pushface.org>]

Lucretia <laguest9000@googlemail.com> writes:

> On Tuesday, 24 September 2019 12:23:30 UTC+1, Optikos  wrote:
>
>> > begin
>> >    A.all ... ; -- raises exception.
>> 
>> No, to be as useful as Rust's borrow checker, instead of raising
>> exception, it needs to be a compile-time error.  The compiler needs
>> to maintain a whole-program directed graph at compile-time, not
>> defer a detection-based localized analysis to run-time.
>
> Yes, the compiler would raise that exception at compile time. This
> idea that all exceptions are raised at runtime is false and you should
> check the AARM.

GNAT could (guessing here, but following the way it handles CE detected
at compile time) raise a *warning* to the effect that an exception ould
be raised at run time. And if compiling with warning => error (-gnatwe)
that would do the job. To an extent.