dip1000 and preview in combine to cause extra safety errors

[Dennis]

On Monday, 13 June 2022 at 23:58:26 UTC, Walter Bright wrote:
> I suggest there is little point to permitting it, as good style 
> would expect that a different variable be used for each 
> purpose, rather than "recycling" an existing variable.

I chose the example for its simplicity, not for its good style. 
The point remains that `scope` checking has false positives and 
it does crop up in real code. Look for example at [this 
refactoring that had to be done in 
Phobos](https://github.com/dlang/phobos/pull/8116/files) because 
`tempCString` deals with pointers to either stack-allocated or 
heap-allocated memory based on the length of a run-time string.

That being said, I wouldn't be against eventually doing `scope` 
checks in `@system` code as long as there's still some kind of 
escape hatch.