Why does intpromote spew warnings for ~ operator?

[Stefan Koch]

On Tuesday, 14 September 2021 at 09:07:24 UTC, Alexey wrote:
>```c
> #include <stdio.h>
>
> int main(int argc, char* argv[])
> {
>     unsigned char a = 0b100;
>     unsigned char b = ~a;
>     return 0;
> }
> ```
> will C also silently promote a to int and silently truncate it 
> to uchar? - should those under-carpet things also happen in D 
> just to save C's behavior?

Yes it will.
you can convince yourself if you run this.

```c
#include <stdio.h>
#include <stdbool.h>

char* binPrint(int v, char* buffer);

#define bits(v) (sizeof(v) * 8)
int main(int argc, char* argv[])
{
     char buffer[bits(int) + 1];

     unsigned char a = 0b100;
     printf("a: %d -- %s\n",  a, binPrint(a, &buffer[0]));

     unsigned char b = ~a;
     unsigned int  c = ~a;
     printf("uchar b: %u -- %s\n",  b, binPrint(b, &buffer[0]));
     printf("uint c: %u -- %s\n",  c, binPrint(c, &buffer[0]));
}

char* binPrint(int v, char* buffer)
{
     int last_set_bit;
     for(int bit_idx = 0; bit_idx < bits(v); bit_idx++)
     {
         bool bit_set = (v & (1 << bit_idx));
         buffer[bits(v) - bit_idx] = bit_set ? '1' : '0';
         if (bit_set) last_set_bit = bit_idx;
     }
     buffer[bits(v) + 1] = '\0';
     return &buffer[bits(v) - last_set_bit];
}
#undef bits
```