DIP1000 scope inference

[Steven Schveighoffer]

On 10/26/22 8:49 AM, Dukc wrote:
> On Wednesday, 26 October 2022 at 08:03:37 UTC, Walter Bright wrote:
>> On 10/24/2022 6:35 PM, Steven Schveighoffer wrote:
>>> In a `@trusted` function today, without dip1000, the above is 
>>> perfectly reasonable and not invalid. Will dip1000 make it corrupt 
>>> memory?
>>
>> A very good question. Clearly, having code work when it is @safe, but 
>> cause memory corruption when it is marked @trusted, is the wrong 
>> solution. This should never happen. I'm not sure what the solution 
>> should be here.
> 
> It's not quite exactly that. The code in question fails with `@safe`.
> 
> The problem is that Steven's `@trusted` code not only happens to work, 
> but is defined behaviour without dip1000, yet undefined behaviour with 
> `-preview=dip1000`.

Yes, maybe. I don't know if it's UB, because I don't know the 
rules/philosophy.

> 
> My proposal: disable local variable `scope` inference for `@system` and 
> `@trusted` code. This has the downside that it's difficult to test 
> whether the implementation really turns the inference off. But unless 
> we're ready to ditch `scope` inference altogether I can't come up with 
> anything better.

This is a possibility. I don't know the consequences of this, especially 
for template code.

-Steve