only parameters or stack-based variables can be `inout`

[Steven Schveighoffer]

On Monday, 25 November 2024 at 14:24:44 UTC, Bastiaan Veelo wrote:

> // Fishy:
> inout(E) gun(inout(E) e)
> {
>     //writeln(e.to!string); // only parameters or stack-based 
> variables can be `inout`
>     writeln((cast(Unqual!E)e).to!string); // OK
>     return e;
> }

Longstanding issue. When inout was first proposed, the point was 
to prevent people from using in nonsensical ways. But this really 
prevents reasonable template usage without all kinds of static 
checks.

I went over this in my 2016 talk: 
https://dconf.org/2016/talks/schveighoffer.html

1. inout should just be allowed to be returned when parameters 
are not inout. The equivalent would just be const.
2. inout member fields should be fine.

-Steve