On Borrow Checking

[Timon Gehr]

On 5/11/25 20:03, Walter Bright wrote:
> On 5/11/2025 4:32 AM, Timon Gehr wrote:
>> Well, it's common enough to need type system support.
> 
> That's not necessarily true.

You had claimed it is not a severe limitation. It's common enough to 
need type system support to not be severely limited.

> You can do everything in C that D does, it's just less convenient.
> ...

Severely so.

> 
>> Support for multiple indirections is also important. Rust actually 
>> provides both of these.
> 
> There are other ways to do that. Multiple indirections can be handled by 
> using structs and then only allowing access to structs through member 
> function interfaces.
> ...

Well, safe dynamic arrays can be handled by creating a custom struct and 
accessing it with API functions that perform bounds checks. Yet C 
programmers rarely do this.

> 
>>> It's a minor inconvenience that can be refactored away.
>> In general you'll have to resort to `@system` code,
> 
> While you can always do it with @system code, I'm not convinced some 
> refactoring won't work. It's not a disaster to use @system code now and 
> then.
> ...

The best you can usually do is to manually move safety checks to 
runtime. The point of a type system in this case is to avoid that 
overhead and to give assurances before the program actually runs or even 
ships to users.

> 
>> and it will stand in the way of other refactorings you may want to do.
> 
> You've got to do a lot of refactoring to make Rust code work anyway.
> ...

The inflexibility of Rust is indeed one of the main points of critique 
that is directed against it.