DIP 1028---Make @safe the Default---Community Review Round 1

[Walter Bright]

On 1/3/2020 3:30 PM, Johan wrote:
> I expect the change of default to be a _lot_ of work to deal with at Weka. I 
> think it will not be easy at all, because there is a lot of templated code and 
> code checking whether something compiles or not (`__traits(compiles)`). Every 
> compiler update changes what compiles and does not compiles, and it is almost 
> always very hard to track down how that changes the behavior of Weka's code. (If 
> something doesn't compile, the error happens in a template that cannot be 
> instantiated because some template 5 layers down is not instantiatable for 
> example. The error won't say that of course...)
> With the @safe change, I'm expecting 100s of templates that will no longer 
> compile or change behavior, and for very few of the compile errors will it be 
> obvious what is going on. As said before, `@system:` is not going to help.

Templates without an explicit @safe/@trusted/@system will still get their safety 
attributes inferred as before.


> I have no opinion on whether this is a good change or not. I just very much 
> would like to get the message across that this change will be very disruptive 
> and so please provide a long deprecation time (e.g. something like 2 years).

That's probably a good idea. Keep in mind that even when it is no longer a 
-preview feature, there'll be a -revert switch there for a long time to continue 
to use the old behavior.

I am interested to hear about your experience with this on Weka's codebase, and 
am open to your advice on the timing.