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\\)#"
MutVisitor::token_visiting_enabled
TreeAndSpacing
#[collapse_debuginfo]
mk_attr_id
ParseSess
AttrVec
crate
&str
String
MultiSpan::push_span_label