syntax: Implement #![no_core]

This commit is an implementation of [RFC 1184][rfc] which tweaks the behavior of
the `#![no_std]` attribute and adds a new `#![no_core]` attribute. The
`#![no_std]` attribute now injects `extern crate core` at the top of the crate
as well as the libcore prelude into all modules (in the same manner as the
standard library's prelude). The `#![no_core]` attribute disables both std and
core injection.

[rfc]: https://github.com/rust-lang/rfcs/pull/1184

1 files changed, 2 insertions, 4 deletions

diff --git a/src/libcollections/lib.rs b/src/libcollections/lib.rs
index ee7d2c4d23b..5fb28d67974 100644
--- a/src/libcollections/lib.rs
+++ b/src/libcollections/lib.rs
@@ -33,9 +33,7 @@
 #![feature(alloc)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
-#![feature(core)]
 #![feature(core_intrinsics)]
-#![feature(core_prelude)]
 #![feature(core_slice_ext)]
 #![feature(core_str_ext)]
 #![feature(heap_api)]
@@ -62,12 +60,12 @@
 #![feature(utf8_error)]
 #![cfg_attr(test, feature(rand, test))]
 #![cfg_attr(not(test), feature(str_words))]
+#![cfg_attr(stage0, feature(core, core_prelude))]
 
 #![feature(no_std)]
 #![no_std]
 
-#[macro_use]
-extern crate core;
+#[cfg(stage0)] #[macro_use] extern crate core;
 
 extern crate rustc_unicode;
 extern crate alloc;