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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.ada
Subject: Re: Implementing Rust's borrow checked pointers
Date: Tue, 24 Sep 2019 12:13:30 -0700
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Date: 2019-09-24T12:13:30-07:00
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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.

Can you provide a specific citation?

Certainly a compiler can diagnose an error at compile time, but I've
never heard that referred to as an "exception".  And a compiler can
generate code that unconditionally raises an exception, but that code is
executed at run time.

(I've seen compile-time exceptions, but they were compiler bugs, not
diagnostics for the program being compiled.)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Will write code for food.
void Void(void) { Void(); } /* The recursive call of the void */