This crate declares the set of past and present unstable features in the compiler.
Feature gate checking itself is done in
at the moment.
Features are enabled in programs via the crate-level attributes of
#![feature(...)] with a comma-separated list of features.
For the purpose of future feature-tracking, once a feature gate is added,
even if it is stabilized or removed, do not remove it. Instead, move the
symbol to the
removed modules respectively.