replaced feature-gate use with cfg_attr

compiler/rustc_ast_passes/src/lib.rs

@@ -4,7 +4,7 @@
 //!
 //! The crate also contains other misc AST visitors, e.g. `node_count` and `show_span`.
 
-#![feature(bindings_after_at)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(iter_is_partitioned)]
 #![feature(box_patterns)]
 #![recursion_limit = "256"]

compiler/rustc_mir/src/lib.rs

@@ -8,7 +8,7 @@ Rust MIR: a lowered representation of Rust.
 #![feature(in_band_lifetimes)]
 #![feature(array_windows)]
 #![feature(assert_matches)]
-#![feature(bindings_after_at)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]

compiler/rustc_parse/src/lib.rs

@@ -2,7 +2,7 @@
 
 #![feature(array_windows)]
 #![feature(crate_visibility_modifier)]
-#![feature(bindings_after_at)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(box_syntax)]
 #![feature(box_patterns)]
 #![recursion_limit = "256"]

compiler/rustc_typeck/src/lib.rs

@@ -56,7 +56,7 @@ This API is completely unstable and subject to change.
 */
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(bindings_after_at)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(bool_to_option)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]