deprecate boolean evaluation of floating point and character types

[Richard (Rikki) Andrew Cattermole]

On 01/05/2024 3:45 PM, Nicholas Wilson wrote:
> On Tuesday, 30 April 2024 at 18:09:22 UTC, Richard (Rikki) Andrew 
> Cattermole wrote:
>> Characters are quite often compared against zero when doing string 
>> handling in C without the binary expression. For this reason I would 
>> not want to see this changed.
> 
> 
> D has the philosophy that valid C code should either behave the same in 
> C as in D, or give an error (c.f. integer promotion rules). It is 
> reasonable to make misleading behaviour like this an error.

Both C and D have the same behavior for characters.

```c
#include <stdio.h>

int main()
{
     char c = 0;

     if (c) {
         printf("+\n");
     }

     return 0;
}
```

No output.

```d
import core.stdc.stdio;

void main()
{
     char c = 0;

     if (c) {
         printf("+\n");
     }
}
```

No output.