-preview switches

[Steven Schveighoffer]

On 4/1/20 3:01 PM, Johan wrote:
> On Wednesday, 1 April 2020 at 14:26:15 UTC, Atila Neves wrote:
>>
>> I think the right way to nudge D programmers to transition to where we 
>> can turn -preview into -revert is to issue deprecation messages for a 
>> while. Nothing like a noisy build to get people to file issues on 
>> github (or even better, PRs) to get this fixed.
> 
> Please note that deprecation messages are effectively errors in a build 
> environment with -de (i.e. Weka). In that case the only workable 
> compilation is to use the new way (i.e. with preview switch). Especially 
> due to deprecation/error messages in speculative code, this can be 
> annoying to deal with.
> What is nice about _not_ showing deprecation messages and instead having 
> only -preview, is that it is easier to switch to a new compiler (which 
> always creates a ton of work already). And then slowly one can enable 
> the preview options to get ready for the future. I do think that putting 
> a date on certain things will help create some urgency to start future 
> proofing code.

I think compiler deprecation messages can be designated as not becoming 
errors for -de.

For example, I'm pretty sure the import changes that were done not too 
long ago had deprecation messages that never resulted in errors.

-Steve