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

16 files changed, 40 insertions, 29 deletions

diff --git a/src/libcore/fmt/builders.rs b/src/libcore/fmt/builders.rs
index 22f0215f0ad..39a067c1608 100644
--- a/src/libcore/fmt/builders.rs
+++ b/src/libcore/fmt/builders.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use prelude::*;
+use prelude::v1::*;
 use fmt::{self, Write, FlagV1};
 
 struct PadAdapter<'a, 'b: 'a> {
diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index 02b23c6c7e7..668e2ecf1c6 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -12,7 +12,7 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-use prelude::*;
+use prelude::v1::*;
 
 use cell::{Cell, RefCell, Ref, RefMut, BorrowState};
 use marker::PhantomData;
diff --git a/src/libcore/fmt/num.rs b/src/libcore/fmt/num.rs
index 7cacc6af575..bffbb789f22 100644
--- a/src/libcore/fmt/num.rs
+++ b/src/libcore/fmt/num.rs
@@ -12,7 +12,7 @@
 
 // FIXME: #6220 Implement floating point formatting
 
-use prelude::*;
+use prelude::v1::*;
 
 use fmt;
 use num::Zero;
diff --git a/src/libcore/hash/mod.rs b/src/libcore/hash/mod.rs
index e35f380d06f..34bc3b835a1 100644
--- a/src/libcore/hash/mod.rs
+++ b/src/libcore/hash/mod.rs
@@ -62,7 +62,7 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-use prelude::*;
+use prelude::v1::*;
 
 use mem;
 
@@ -183,7 +183,7 @@ pub fn hash<T: Hash, H: Hasher + Default>(value: &T) -> u64 {
 //////////////////////////////////////////////////////////////////////////////
 
 mod impls {
-    use prelude::*;
+    use prelude::v1::*;
 
     use slice;
     use super::*;
diff --git a/src/libcore/hash/sip.rs b/src/libcore/hash/sip.rs
index 93bdadff549..4dcd513a0d2 100644
--- a/src/libcore/hash/sip.rs
+++ b/src/libcore/hash/sip.rs
@@ -10,8 +10,9 @@
 
 //! An implementation of SipHash 2-4.
 
+use prelude::v1::*;
+
 use ptr;
-use prelude::*;
 use super::Hasher;
 
 /// An implementation of SipHash 2-4.
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 238644c4a26..56fb4c71a6a 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -60,8 +60,10 @@
        html_playground_url = "http://play.rust-lang.org/")]
 #![doc(test(no_crate_inject))]
 
-#![feature(no_std)]
-#![no_std]
+#![cfg_attr(stage0, feature(no_std))]
+#![cfg_attr(stage0, no_std)]
+#![cfg_attr(not(stage0), feature(no_core))]
+#![cfg_attr(not(stage0), no_core)]
 #![allow(raw_pointer_derive)]
 #![deny(missing_docs)]
 
@@ -168,6 +170,7 @@ mod tuple;
 // compiling the core library when it's compiling this library, so it expands
 // all references to `::core::$foo`
 #[doc(hidden)]
+#[cfg(stage0)]
 mod core {
     pub use intrinsics;     // derive(PartialOrd)
     pub use fmt;            // format_args!
diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs
index 6b4424093b4..d0e6d4fa49c 100644
--- a/src/libcore/num/f32.rs
+++ b/src/libcore/num/f32.rs
@@ -15,7 +15,7 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-use prelude::*;
+use prelude::v1::*;
 
 use intrinsics;
 use mem;
diff --git a/src/libcore/num/f64.rs b/src/libcore/num/f64.rs
index fa7aa2ab5ce..bf7da04f995 100644
--- a/src/libcore/num/f64.rs
+++ b/src/libcore/num/f64.rs
@@ -15,7 +15,7 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-use prelude::*;
+use prelude::v1::*;
 
 use intrinsics;
 use mem;
diff --git a/src/libcore/num/flt2dec/bignum.rs b/src/libcore/num/flt2dec/bignum.rs
index 4f373c16f7c..1e39c53f9e0 100644
--- a/src/libcore/num/flt2dec/bignum.rs
+++ b/src/libcore/num/flt2dec/bignum.rs
@@ -21,7 +21,8 @@
 
 #![macro_use]
 
-use prelude::*;
+use prelude::v1::*;
+
 use mem;
 use intrinsics;
 
@@ -351,7 +352,7 @@ define_bignum!(Big32x36: type=Digit32, n=36);
 // this one is used for testing only.
 #[doc(hidden)]
 pub mod tests {
-    use prelude::*;
+    use prelude::v1::*;
     define_bignum!(Big8x3: type=u8, n=3);
 }
 
diff --git a/src/libcore/num/flt2dec/decoder.rs b/src/libcore/num/flt2dec/decoder.rs
index f98bc11a315..a292ffa2e9d 100644
--- a/src/libcore/num/flt2dec/decoder.rs
+++ b/src/libcore/num/flt2dec/decoder.rs
@@ -10,7 +10,7 @@
 
 //! Decodes a floating-point value into individual parts and error ranges.
 
-use prelude::*;
+use prelude::v1::*;
 
 use {f32, f64};
 use num::{Float, FpCategory};
diff --git a/src/libcore/num/flt2dec/mod.rs b/src/libcore/num/flt2dec/mod.rs
index f3a7e8f09a9..40fa2a5563d 100644
--- a/src/libcore/num/flt2dec/mod.rs
+++ b/src/libcore/num/flt2dec/mod.rs
@@ -129,7 +129,7 @@ functions.
 #![unstable(feature = "flt2dec",
             reason = "internal routines only exposed for testing")]
 
-use prelude::*;
+use prelude::v1::*;
 use i16;
 use num::Float;
 use slice::bytes;
diff --git a/src/libcore/num/flt2dec/strategy/dragon.rs b/src/libcore/num/flt2dec/strategy/dragon.rs
index a1137789371..b03286ddd0d 100644
--- a/src/libcore/num/flt2dec/strategy/dragon.rs
+++ b/src/libcore/num/flt2dec/strategy/dragon.rs
@@ -15,7 +15,8 @@ Almost direct (but slightly optimized) Rust translation of Figure 3 of [1].
     quickly and accurately. SIGPLAN Not. 31, 5 (May. 1996), 108-116.
 */
 
-use prelude::*;
+use prelude::v1::*;
+
 use num::Float;
 use cmp::Ordering;
 
diff --git a/src/libcore/num/flt2dec/strategy/grisu.rs b/src/libcore/num/flt2dec/strategy/grisu.rs
index 54d3c92eca4..390920a354c 100644
--- a/src/libcore/num/flt2dec/strategy/grisu.rs
+++ b/src/libcore/num/flt2dec/strategy/grisu.rs
@@ -16,7 +16,8 @@ Rust adaptation of Grisu3 algorithm described in [1]. It uses about
     accurately with integers. SIGPLAN Not. 45, 6 (June 2010), 233-243.
 */
 
-use prelude::*;
+use prelude::v1::*;
+
 use num::Float;
 
 use num::flt2dec::{Decoded, MAX_SIG_DIGITS, round_up};
diff --git a/src/libcore/prelude/mod.rs b/src/libcore/prelude/mod.rs
new file mode 100644
index 00000000000..b6c93615378
--- /dev/null
+++ b/src/libcore/prelude/mod.rs
@@ -0,0 +1,13 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The libcore prelude
+
+pub mod v1;
diff --git a/src/libcore/prelude.rs b/src/libcore/prelude/v1.rs
index ac153d64ab2..50dc9b7e043 100644
--- a/src/libcore/prelude.rs
+++ b/src/libcore/prelude/v1.rs
@@ -11,18 +11,8 @@
 //! The core prelude
 //!
 //! This module is intended for users of libcore which do not link to libstd as
-//! well. This module is not imported by default, but using the entire contents
-//! of this module will provide all of the useful traits and types in libcore
-//! that one would expect from the standard library as well.
-//!
-//! There is no method to automatically inject this prelude, and this prelude is
-//! a subset of the standard library's prelude.
-//!
-//! # Example
-//!
-//! ```ignore
-//! use core::prelude::*;
-//! ```
+//! well. This module is imported by default when `#![no_std]` is used in the
+//! same manner as the standard library's prelude.
 
 #![unstable(feature = "core_prelude",
             reason = "the libcore prelude has not been scrutinized and \
diff --git a/src/libcore/str/pattern.rs b/src/libcore/str/pattern.rs
index 2b3fc39fc8b..10ef689ba5d 100644
--- a/src/libcore/str/pattern.rs
+++ b/src/libcore/str/pattern.rs
@@ -16,7 +16,8 @@
 #![unstable(feature = "pattern",
             reason = "API not fully fleshed out and ready to be stabilized")]
 
-use prelude::*;
+use prelude::v1::*;
+
 use cmp;
 use usize;