Deprecate implicit conversion between signed and unsigned integers

[Walter Bright]

On 2/17/2025 7:07 AM, Paul Backus wrote:
> On Monday, 17 February 2025 at 09:01:45 UTC, Walter Bright wrote:
>> @safe only bans memory corruption. 2's complement arithmetic is not UB.
> 
> Dividing an integer by zero is UB according to the D spec [1], and it is allowed 
> in @safe code.
> 
> [1] https://dlang.org/spec/expression.html#division

That's correct. But it's not memory corruption, and requiring casts doesn't 
address it.

The usual result is a signal is generated. These can be intercepted at the 
user's discretion.

The compiler will flag an error if it can statically determine that the divisor 
is zero. Runtime checks could be added, but since other languages don't do that, 
it would put D at a competitive disadvantage.

As always, there are tradeoffs.