Deprecate implicit conversion between signed and unsigned integers

[An Pham]

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.
>

Just focus on sign vs unsign is not good enough. Sometime you 
need to specify a range of values. There is module std.CheckedInt 
which
1. Should extend it to be a runtime system module which does not 
need to 'import'
2. Add range template parameters Checked!(int, X, Y, ...) like 
Checked!(int, -5, 200, ...)
which only hold values from -5 to 200 inclusively
3. Extend language to allow implicit passing parameter void 
foo(Checked!(int, X, Y, ...) z)
and can be called by foo(10) is ok but foo(1000) should failed