Try blocks are trying

[FeepingCreature]

On Sunday, 10 October 2021 at 16:12:31 UTC, Carl Sturtivant wrote:
> Why is it that a try block is defined to establish a scope?
>
> ```
>     try {
>         auto x = frgl();
>     }
>     // ...
>     // x undefined here
>
> ```
> What is the benefit of this? If try (like static if/foreach) 
> did NOT establish a scope, then this annoyance would go away. 
> And if a scope was desired for some reason, then an extra pair 
> of braces could be written within.
>
> Right now rewriting the above requires getting the return type 
> of frgl and declaring x to be of that type before the try block.
>
> Design error?

I do not deny that my heart has greatly desired this.

Proposal:

```
export try {
     auto x = frgl();
}
catch (Exception) {
     return false;
}
```

shall be equivalent to

```
typeof(frgl()) x = void;
try {
     frgl().moveEmplace(x);
}
catch (Exception) {
     __EXCEPTION_BODY__
     assert(false, "`export` specified: all catch blocks must exit 
scope");
}
POST
```

Here, `auto frgl` dominates `POST` and is thus correct.

Scope guards directly in `try{}` should be lifted into the 
surrounding context, but this is confusing, so they are an error.