first draft Reducing the legal permutations of ref-return-scope

[Sönke Ludwig]

Am 13.05.2025 um 06:23 schrieb Walter Bright:
> https://github.com/WalterBright/documents/blob/master/ReturnRefScope.md

 > This will break existing code. Hence enabling it will be behind a 
-preview=return switch, and will be the default in a future edition.

This should really also emit a deprecation warning without the preview 
switch.

Most preview switches are more or less useless as soon as external 
libraries come into play (which even includes Phobos often enough). My 
guess would be that the effect of this would probably close to zero 
before this is actually available as an edition, meaning more code that 
will fail later gets written in the meantime.