RFC: 2 enhancement DIPs that need feedback

[Basile B.]

On Wednesday, 21 May 2025 at 04:55:50 UTC, Walter Bright wrote:
> On 5/14/2025 9:56 AM, Timon Gehr wrote:
>> Go ahead and implement it. It's harder, not a simplification. 
>> Suddenly, whenever you are parsing any expression, you will 
>> have to take into account the possibility that it is actually 
>> a variable declaration. The way DMD deals with lvalues is also 
>> ill-equipped to allow this to be added easily. Furthermore, 
>> you now have to do proper scope handling for short-circuiting 
>> operations.
>
> There's also a problem with handling destruction of the 
> declaration.

I dont think so. I consider that, based on default 
initialization, which has to always happen, even if an AndAnd LHS 
has evaluated to true and then that the RHS is a VarDeclExp, then 
its matching variable is always destructible.

To be clear the AST for

```d
if (MyStruct ms0 = call0) && (MyStruct ms1 == call1) {}
```

is to be thought as

```d
{
     MyStruct ms0; // def init, ms0 is in valid state
     MyStruct ms1; // def init, ms1 is in valid state
     if (ms0 = call0) && (ms1 == call1) {}
     // ...
     // right before the end of the scope
     ms0.__dtor();
     ms1.__dtor();
}
```

In practice that scenario almost never happen, since VarDeclExp 
are 99% of the time used for pointers or simple numeric types.