Why both isSafe and isUnsafe?

[Steven Schveighoffer]

On 9/27/20 11:00 PM, Andrei Alexandrescu wrote:
> https://dlang.org/phobos/std_traits.html#isSafe
> https://dlang.org/phobos/std_traits.html#isUnsafe
> 
> Implementation:
> 
> template isUnsafe(alias func)
> {
>      enum isUnsafe = !isSafe!func;
> }
> 
> Why do we need both?

They were both added in one PR. 10 years ago.

Probably don't need both. But just undocument the second, and leave it. 
It's not a harm to leave it in and then it won't break code. Can also 
now be shrunk to a short form:

enum isUnsafe(alias func) = !isSafe!func;

-Steve