-preview=in might break code

[Iain Buclaw]

On Monday, 5 October 2020 at 07:55:57 UTC, Walter Bright wrote:
> On 10/4/2020 7:19 AM, Iain Buclaw wrote:
>> I've also skimmed past a passing concern that the ABI between 
>> compilers would be different.  Well, let me rest assure you 
>> that DMD, GDC and LDC have never been compatible in the first 
>> place, so there's no point worrying about that now.
>
> The problem is not dmd compiled code calling gdc/ldc compiled 
> code. The problem is code that works with one compiler fails 
> with another, because the "to ref or not to ref" decision is 
> *implementation defined*.

Furthermore, NRVO is implementation defined, which results in the 
same dmd/gdc/ldc making different decisions for "to ref or not to 
ref", and yet I see no one complaining about that.