-preview=in might break code

[Timon Gehr]

On 05.10.20 09:56, Iain Buclaw wrote:
> 
> 
> Correct me if I'm wrong, but it looks like we'll have three competing 
> implementations:
> 
> DMD: `const scope`, with `ref` applied on types usually passed in memory.
> LDC: `const scope ref @restrict`
> GDC: `const scope` with `ref` applied on types usually passed by 
> invisible reference.

Weren't there different rules for non-POD types? Do those differ between 
backends?

Also, it looks like in this case `__traits(isRef, ...)` will return 
different results with different compiler backends and aliasing `in` 
parameters is UB with LDC? Is `@restrict` wrongly treated as `@safe` or 
does the `@safe`ty of `in` parameters depend on the compiler backend?