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, 1 insertions, 0 deletions

diff --git a/src/libstd/sys/common/thread_local.rs b/src/libstd/sys/common/thread_local.rs
index 3b2cb00d8c4..2269a053874 100644
--- a/src/libstd/sys/common/thread_local.rs
+++ b/src/libstd/sys/common/thread_local.rs
@@ -58,6 +58,7 @@
 #![unstable(feature = "thread_local_internals")]
 #![allow(dead_code)] // sys isn't exported yet
 
+#[cfg(stage0)]
 use prelude::v1::*;
 
 use sync::atomic::{self, AtomicUsize, Ordering};