Let's get the semantic around closure fixed.

[Jesse Phillips]

On Tuesday, 18 May 2021 at 16:47:03 UTC, deadalnix wrote:
> Long story short: https://issues.dlang.org/show_bug.cgi?id=21929
>
> Closure do not respect scope the way they should. Let's fix it.

After Walter's post I definitely see what is happening.


```dlang
for (int i = 0; i < 10; i++) {
         int index = i;
         dgs ~= () {
             import std.stdio;
             writeln(index);
         };
     }
```

When this loop concludes, the value of `i` is 10 and the value of 
index is 9 (as shown from your output).

This is because within the `for` logic `i` was increased and it 
determined `10 < 10` is false. This means the `for`body is not 
executed again leaving `index` at 9.

I don't know why compiler magic you would expect is "correct" 
here. We can't say `i` should be 9 as the loop would not have 
exited then. We certainly don't want `index` to be 10 as that 
would mean the loop expected on more time than it was defined to.


Untested

```dlang
auto i;
auto index;
for (i = 0; i < 10; i++) {
         index = i;
         dgs ~= () {
             import std.stdio;
             writeln(i);
             writeln(index);
         };
    }
```