[RFC] Throwing an exception with null pointers

[Derek Fawcus]

On Wednesday, 16 April 2025 at 22:43:24 UTC, Derek Fawcus wrote:
> ```
> $ clang-14 -Wall -Wnullable-to-nonnull-conversion -c ttt.c
> ttt.c:37:8: warning: implicit conversion from nullable pointer 
> 'int * _Nullable' to non-nullable pointer type 'int * _Nonnull' 
> [-Wnullable-to-nonnull-conversion]
>         ptr = arg3;
>               ^
> ttt.c:41:20: warning: implicit conversion from nullable pointer 
> 'int * _Nullable' to non-nullable pointer type 'int * _Nonnull' 
> [-Wnullable-to-nonnull-conversion]
>         a += *someNonNull(arg3);
>                           ^
> ttt.c:29:16: warning: variable 'ptr' set but not used 
> [-Wunused-but-set-variable]
>         int * NONNULL ptr;
>                       ^
> 3 warnings generated.
> ```

Having now got this to complain in the desired fashion, I'll now 
be applying it to some code at work.  More help in quashing 
sources of bugs.