We all get nullability wrong sometimes

[Asadbek]

On Thursday, 9 July 2026 at 14:33:54 UTC, Richard (Rikki) Andrew 
Cattermole wrote:
> Here is a nice little showcase of what the fast DFA engine is 
> able to do:
>
> ``class IdentExpr``
>
> https://github.com/higgsjs/Higgs/blob/master/source/parser/ast.d#L986
>
> ```d
>             catchIdent = cast(IdentExpr)parseExpr(input);
>             if (catchIdent is null)
>                 throw new ParseError("invalid catch 
> identifier", catchIdent.pos);
> ```
>
> https://github.com/higgsjs/Higgs/blob/master/source/parser/parser.d#L462
>
> Anyone notice a slight problem with this code?
>
> While a sound static analyser would be nice, being able to 
> catch code like this does mean bugs don't sit around for 10+ 
> years in production code, just waiting to give someone a very 
> bad day.
>
> https://github.com/higgsjs/Higgs/issues/219

I have just checked dmd repository and it appears dmd compiler 
has custom data flow analysis optimizations. That is really great!

Is DFA analysis proving that the `catchIdent` is `null` and 
therefore catching what would be a runtime error at compile time ?