@phan-immutable

The @phan-immutable tag declares a class as immutable. Phan documents it as an alias of @phan-read-only (see phan-read-only-tag.md); this component's own not-yet-implemented equivalent for the same concept is @immutable.

This library recognizes it as an alias: it parses identically to the canonical tag above and produces the exact same tag instance, keeping the vendor-prefixed name it was written with.