Comparing Exceptions and Errors

[frame]

On Tuesday, 7 June 2022 at 18:37:13 UTC, Steven Schveighoffer 
wrote:

>
> My very common use of `scope(failure)` for my DB code:
>
> ```d
> conn.exec("START TRANSACTION");
> scope(success) conn.exec("COMMIT");
> scope(failure) conn.exec("ROLLBACK");
> ```
>
> This is hard to encapsulate into a type, as dtors only hook 
> `scope(exit)` essentially.
>
> -Steve

That's fine as the Throwable is still thrown but since 
`scope(failure)` acts as like catch-block, people may use it as 
replacement if there is something more to do.

I personally like the clean, short syntax when I don't care about 
the actual exception or if I know the called function has already 
handled the exception and just rethrows it:

```d
bool fun() {
      scope(failure) {
          // do something
          return false;
      }

      badCode();
      return true;
}
```

I know this is bad as I'm capturing a possible error here - but 
this is what an unexperienced coder would do, because it works. 
The better approach would be to use `scope(exception)`  (not 
typed, just as keyword) that allows to act only on Exceptions so 
one cannot break Exception vs Error paradigma and this also 
clarifies that usage of `scope(failure)` is potentially dangerous 
if you return from it.

Anyway, I just put that here - maybe you mention it in your blog.