`in` on function parameters: const, scope const, ref scope const ?

[Petar]

On Friday, 3 April 2020 at 06:19:38 UTC, Mathias LANG wrote:
> [..]

One more thought:

`in` needs be its own parameter storage class, like `out` and 
`ref` on the name-mangling / ABI level. This is the only way to 
change its meaning while preserving it in compiler-generated *.di 
headers and preventing subtle errors while linking different 
libraries compiled with and without the preview switch.