Can we fix this?

[jfondren]

On Wednesday, 29 September 2021 at 10:44:53 UTC, Imperatorn wrote:
> https://issues.dlang.org/show_bug.cgi?id=2043
>
> Impossible?

... Documentation:

D has two kinds of blocks, the `{ ... }` kind and the `(){ ... 
}();` kind. Within the former, for efficiency, [something about 
this bug]. Within the latter, closure environments will be as 
expected from other languages at the cost of additional 
allocation. These "bubble blocks" are admittedly ugly but this is 
part of D's firm stand against the programming practices of the 
Scheme community.

```d
void delegate()[] dgList;

void main() {
     import std.stdio : writeln;

     foreach(int i; [1, 2, 3]) {
         auto b = i+2;
         dgList ~= { writeln(b); };
         writeln(&b); // b will be the *same* on each iteration
     }
     foreach (dg; dgList)
         dg(); // output: 5 5 5
}
```

vs.

```d
void delegate()[] dgList;

void main() {
     import std.stdio : writeln;

     foreach(int i; [1, 2, 3]) (){
         auto b = i+2;
         dgList ~= { writeln(b); };
         writeln(&b); // b will be *unique* on each iteration
     }();
     foreach (dg; dgList)
         dg(); // output: 3 4 5
}
```