[nll] librustc_typeck: enable feature(nll) for bootstrap

src/librustc_typeck/lib.rs

@@ -76,6 +76,7 @@ This API is completely unstable and subject to change.
 #![feature(crate_visibility_modifier)]
 #![feature(exhaustive_patterns)]
 #![feature(iterator_find_map)]
+#![cfg_attr(not(stage0), feature(nll))]
 #![feature(quote)]
 #![feature(refcell_replace_swap)]
 #![feature(rustc_diagnostic_macros)]