Do Loop with Variable

[Quirin Schroll]

On Thursday, 17 July 2025 at 13:43:33 UTC, Dukc wrote:
> On Tuesday, 8 July 2025 at 16:40:24 UTC, Quirin Schroll wrote:
>> I have the feeling this isn’t gonna fly, but I’ll say it 
>> anyways because maybe someone finds a solution.
>> ```d
>> do (int x = 0)
>> { }
>> while (++x < 10);
>> ```
>> which would be equivalent to
>> ```d
>> {
>>     int x = 0;
>>     do
>>     { }
>>     while (++x < 10);
>> }
>> ```
>
> I would probably prefer if symbols declared inside the do 
> statement would be accessible in the condition. Would be a 
> breaking change though, requiring a warning from the compiler 
> if a symbol declared both inside and outside the do block would 
> be used in `while` and probably doing it over an edition switch.

Realistically, if you reference a symbol that’s defined within 
the loop in the condition that coincidentally resolves because 
it’s *also* defined in the outer scope, that should be an error. 
You can always refer to such a symbol in an unambiguous way. 
Here’s what I mean:
```d
struct S
{
     int x;
     void f()
     {
         do { int x; …; }
         while (x > 0); // likely a bug
     }
}
```
The `x` in `x > 0` refers to `this.x`, not the local variable 
defined in the loop. My sense is: No-one actually writes such 
code intentionally. If it really makes sense to name a 
`do`-loop-body variable the same as an outer-scope variable used 
in its condition, it’s not too much to ask to make this clear: 
Use `this.x` or `.x` (global) or whatever. (I filed this as an 
issue.)