[Issue 23175] -preview=in silently adds possible stack memory escape

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23175

Richard Cattermole <alphaglosined at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |alphaglosined at gmail.com

--- Comment #10 from Richard Cattermole <alphaglosined at gmail.com> ---
(In reply to Mathias LANG from comment #9)
> > I do not think we need to change the semantics of preview=in, or to disable optimizations based on it. What we need is a warning to tell the user that what he wrote before, while valid with the previous compiler, has memory corruption implications now that the semantics have changed.
> 
> You should have led with this. That's what `-transition` is for. It lists
> all instances of `in` usage so you can inspect them.

```
  -transition=<name>
                    help with language change identified by 'name'
```

That description could do with some improvement.

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