A Philosophy of Software Design

[Richard (Rikki) Andrew Cattermole]

On 24/05/2026 4:10 PM, Walter Bright wrote:
> Invalid code nodes are replaced with "Error" nodes. This worked far 
> better than I anticipated. No exceptions are thrown. It also behaves 
> like NaN.

That's not actually how you handled it, although I'm sure it solved some 
problems much more easily.

You handled it by checking the error count. In other words a global flag.

https://github.com/dlang/dmd/blob/3c2ad72ad3be9c38c76569ccd1574e39fec2256d/compiler/src/dmd/typesem.d#L4787

https://github.com/dlang/dmd/blob/3c2ad72ad3be9c38c76569ccd1574e39fec2256d/compiler/src/dmd/globals.d#L368

If you can get an error node without an error message that is an ICE 
that should have been emitted but wasn't.