I thought defer and lambdas weren't making it to C23...
Everything that is not part of C23 I annotated with "extension". For instance "Extension Defer" or "Extension Lambda" are not part of C23.
Iirc NarcissiusJS was a test-bed for future JS features at a time when development was a bit slow that allowed quick prototypes.
https://github.com/mozilla/narcissus https://wiki.mozilla.org/Narcissus