On Borrow Checking

[Clouudy]

On Sunday, 11 May 2025 at 20:43:52 UTC, Paul Backus wrote:
> The reason for the negativity is that people do not want "a 
> borrow checker." What they want is more powerful safety 
> analysis. A borrow checker is merely one possible means of 
> achieving that goal.
>
> In business terms, this is a failure of "product-market fit." 
> You are supplying something that there is no demand for. Even 
> if it works perfectly, nobody is going to buy it.

I don't necessarily believe that the issue is "nobody wants a 
borrow checker", because @nogc people would definitely like 
having something similar to it, or to smart pointers. But the 
issue is that it seems like whenever the D Devs decide to work on 
new features they immediately get distracted by a different shiny 
new thing before anything is completely finished.

There was C++ interoperability, which doesn't completely work 
because of inheritance (and probably other reasons, too). Then 
there's ImportC, which doesn't work with macros because D doesn't 
have a pre-processor (not that I would support one being included 
in normal D, but if the goal is to let you just include C files, 
you probably need it for C things). There was obviously @nogc 
features scattered all around, and there's still @safe which 
blocks some code that is actually safe. Allocators are still 
around but nobody in the DLF wants to keep them (which I disagree 
with).

And right now there's a debate about changing Phobos and how it 
should happen, but there hasn't been any visible progress on 
actually implementing it. Now we're adding borrow-checking that 
doesn't work in a familiar manner to the most famous 
implementation of it?

IMO there needs to be a temporary freeze on new features until 
everything that is currently in the language and is incomplete 
gets complete. Then decide on whether we want a borrow checker or 
whether we want smart pointers (or both), then decide on whether 
we want to keep allocators or try different memory management 
methods, and so on. It doesn't really inspire much confidence to 
hear "well most of this feature works but there are exceptions", 
and a lot of people don't use D because of stuff like that.