librustc: Put `#[unsafe_destructor]` behind a feature gate.

Closes #8142.

This is not the semantics we want long-term. You can continue to use
`#[unsafe_destructor]`, but you'll need to add
`#![feature(unsafe_destructor)]` to the crate attributes.

[breaking-change]

1 files changed, 3 insertions, 1 deletions

diff --git a/src/libnative/lib.rs b/src/libnative/lib.rs
index 24f1b9b9407..b44673a24ef 100644
--- a/src/libnative/lib.rs
+++ b/src/libnative/lib.rs
@@ -52,15 +52,17 @@
 #![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "http://www.rust-lang.org/favicon.ico",
        html_root_url = "http://doc.rust-lang.org/")]
+
 #![deny(unused_result, unused_must_use)]
 #![allow(non_camel_case_types)]
 #![allow(deprecated)]
+#![allow(unknown_features)] // NOTE: remove after a stage0 snap
 #![feature(default_type_params)]
 
 // NB this crate explicitly does *not* allow glob imports, please seriously
 //    consider whether they're needed before adding that feature here (the
 //    answer is that you don't need them)
-#![feature(macro_rules)]
+#![feature(macro_rules, unsafe_destructor)]
 
 extern crate alloc;
 extern crate libc;