std: Add a new top-level thread_local module

This commit removes the `std::local_data` module in favor of a new
`std::thread_local` module providing thread local storage. The module provides
two variants of TLS: one which owns its contents and one which is based on
scoped references. Each implementation has pros and cons listed in the
documentation.

Both flavors have accessors through a function called `with` which yield a
reference to a closure provided. Both flavors also panic if a reference cannot
be yielded and provide a function to test whether an access would panic or not.
This is an implementation of [RFC 461][rfc] and full details can be found in
that RFC.

This is a breaking change due to the removal of the `std::local_data` module.
All users can migrate to the new thread local system like so:

    thread_local!(static FOO: Rc<RefCell<Option<T>>> = Rc::new(RefCell::new(None)))

The old `local_data` module inherently contained the `Rc<RefCell<Option<T>>>` as
an implementation detail which must now be explicitly stated by users.

[rfc]: https://github.com/rust-lang/rfcs/pull/461
[breaking-change]

src/test/auxiliary/plugin_crate_outlive_expansion_phase.rs

@@ -15,6 +15,7 @@
 extern crate rustc;
 
 use std::any::Any;
+use std::cell::RefCell;
 use rustc::plugin::Registry;
 
 struct Foo {
@@ -27,7 +28,7 @@ impl Drop for Foo {
 
 #[plugin_registrar]
 pub fn registrar(_: &mut Registry) {
-    local_data_key!(foo: Box<Any+Send>);
-    foo.replace(Some(box Foo { foo: 10 } as Box<Any+Send>));
+    thread_local!(static FOO: RefCell<Option<Box<Any+Send>>> = RefCell::new(None));
+    FOO.with(|s| *s.borrow_mut() = Some(box Foo { foo: 10 } as Box<Any+Send>));
 }
 

src/test/compile-fail/core-tls-store-pointer.rs

@@ -1,16 +0,0 @@
-// Copyright 2012 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.
-
-// Testing that we can't store a reference in task-local storage
-
-local_data_key!(key: Box<&int>)
-//~^ ERROR missing lifetime specifier
-
-fn main() {}

src/test/compile-fail/macro-local-data-key-priv.rs

@@ -11,10 +11,10 @@
 // check that the local data keys are private by default.
 
 mod bar {
-    local_data_key!(baz: f64)
+    thread_local!(static baz: f64 = 0.0)
 }
 
 fn main() {
-    bar::baz.replace(Some(-10.0));
+    bar::baz.with(|_| ());
     //~^ ERROR static `baz` is private
 }

src/test/run-pass/macro-local-data-key.rs

@@ -1,26 +0,0 @@
-// Copyright 2013 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.
-
-local_data_key!(foo: int)
-
-mod bar {
-    local_data_key!(pub baz: f64)
-}
-
-pub fn main() {
-    assert!(foo.get().is_none());
-    assert!(bar::baz.get().is_none());
-
-    foo.replace(Some(3));
-    bar::baz.replace(Some(-10.0));
-
-    assert_eq!(*foo.get().unwrap(), 3);
-    assert_eq!(*bar::baz.get().unwrap(), -10.0);
-}

src/test/run-pass/panic-during-tld-destroy.rs

@@ -1,33 +0,0 @@
-// Copyright 2014 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.
-
-use std::task;
-
-static mut DROPS: uint = 0;
-
-struct Foo;
-impl Drop for Foo {
-    fn drop(&mut self) {
-        unsafe { DROPS += 1; }
-        panic!()
-    }
-}
-
-fn main() {
-    let _ = task::try(proc() {
-        local_data_key!(foo: Foo);
-        foo.replace(Some(Foo));
-    });
-
-    unsafe {
-        assert_eq!(DROPS, 1);
-    }
-}
-

src/test/run-pass/running-with-no-runtime.rs

@@ -17,8 +17,6 @@ use std::rt;
 
 use rustrt::unwind::try;
 
-local_data_key!(foo: int)
-
 #[start]
 fn start(argc: int, argv: *const *const u8) -> int {
     if argc > 1 {
@@ -30,8 +28,6 @@ fn start(argc: int, argv: *const *const u8) -> int {
                 4 => assert!(try(|| panic!()).is_err()),
                 5 => assert!(try(|| spawn(proc() {})).is_err()),
                 6 => assert!(Command::new("test").spawn().is_err()),
-                7 => assert!(foo.get().is_none()),
-                8 => assert!(try(|| { foo.replace(Some(3)); }).is_err()),
                 _ => panic!()
             }
         }
@@ -57,10 +53,6 @@ fn main() {
     pass(Command::new(me).arg(x).output().unwrap());
     let x: &[u8] = &[6u8];
     pass(Command::new(me).arg(x).output().unwrap());
-    let x: &[u8] = &[7u8];
-    pass(Command::new(me).arg(x).output().unwrap());
-    let x: &[u8] = &[8u8];
-    pass(Command::new(me).arg(x).output().unwrap());
 }
 
 fn pass(output: ProcessOutput) {