Actually even worse, it seems to be just a literal
As an example, the
mbox crate uses 7 features in the nightly channel*, but the raw data only lists
placement_in_syntax because there is a
#![feature(placement_in_syntax)] in the doc comment.
I guess this also explains @jethrogb's odd findings, maybe the script hint a literal
#![feature(...)] in the comments.
(The 7 features are: specialization, unique, unsize, coerce_unsized, placement_new_protocol, placement_in_syntax, box_syntax)