Deprecate implicit conversion between signed and unsigned integers

[Dom DiSc]

On Monday, 3 February 2025 at 18:40:20 UTC, Atila Neves wrote:
> https://forum.dlang.org/post/pbhjffbxdqpdwtmcbikh@forum.dlang.org
>
> On Sunday, 12 May 2024 at 13:32:36 UTC, Paul Backus wrote:
>> D inherited these implicit conversions from C and C++, where 
>> they are widely regarded as a source of bugs.
>>
>> [...]
>
> My bias is to not like any implicit conversions of any kind, 
> but I'm not sure I can convince Walter of that.

I think most of the problems with these implicit conversions 
would be gone if we make this work:

```d
    byte a= -5;
    ulong b = 1_000_000_000_000;
    assert(a < b); // fails
```

And we already do have a solution for this (see 
https://issues.dlang.org/show_bug.cgi?id=259), but Walter refuses 
it, because it will break code that relies on this bug.
How much less likely is it to convince him of your proposal?