On later stages, the feature is already stable. Result of running: rg -l "feature.let_else" compiler/ src/librustdoc/ library/ | xargs sed -s -i "s#\\[feature.let_else#\\[cfg_attr\\(bootstrap, feature\\(let_else\\)#"
RefCell
TransitiveRelation
lazy::Sync{OnceCell,Lazy}
sync::{Once,Lazy}Lock
rustc_data_structures::thin_vec::ThinVec
thin_vec::ThinVec
into_iter
drain(..)
Encodable
Encoder
Queries::new