Deprecate implicit conversion between signed and unsigned integers

[Walter Bright]

On 2/17/2025 1:06 AM, Atila Neves wrote:
>> (Did I mention that explicit casts also hide errors introduced by refactoring?)
> 
> `cast(typeof(foo)) bar`?

That can work, but when best practices mean adding more code, the result is 
usually failure.

Also, what if `foo` changes to something not anticipated by that cast?