-preview=in might break code

[Walter Bright]

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*.