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

2 files changed, 5 insertions, 0 deletions

diff --git a/src/libstd/thread/local.rs b/src/libstd/thread/local.rs
index 9a6d68acb9f..a6ecd2d88d2 100644
--- a/src/libstd/thread/local.rs
+++ b/src/libstd/thread/local.rs
@@ -12,6 +12,7 @@
 
 #![unstable(feature = "thread_local_internals")]
 
+#[cfg(stage0)]
 use prelude::v1::*;
 
 use cell::UnsafeCell;
@@ -271,6 +272,7 @@ impl<T: 'static> LocalKey<T> {
           not(no_elf_tls)))]
 #[doc(hidden)]
 mod imp {
+    #[cfg(stage0)]
     use prelude::v1::*;
 
     use cell::{Cell, UnsafeCell};
diff --git a/src/libstd/thread/scoped_tls.rs b/src/libstd/thread/scoped_tls.rs
index cf2c5db8277..1ea33a01791 100644
--- a/src/libstd/thread/scoped_tls.rs
+++ b/src/libstd/thread/scoped_tls.rs
@@ -42,6 +42,7 @@
 
 #![unstable(feature = "thread_local_internals")]
 
+#[cfg(stage0)]
 use prelude::v1::*;
 
 #[doc(hidden)]
@@ -249,6 +250,7 @@ mod imp {
           no_elf_tls))]
 #[doc(hidden)]
 mod imp {
+    #[cfg(stage0)]
     use prelude::v1::*;
 
     use cell::Cell;
@@ -278,6 +280,7 @@ mod imp {
 #[cfg(test)]
 mod tests {
     use cell::Cell;
+    #[cfg(stage0)]
     use prelude::v1::*;
 
     scoped_thread_local!(static FOO: u32);