The previous version of the chapter covered a lot of ground, but was a little
meandering and hard to follow at times. This draft is intended to be clearer
and more direct, while still providing the same information as the previous
version.

The book's "Error handling with Box<Error>" section talks about Box<Error>.
In the actual example Box<Error + Send + Sync> is used instead so that the
corresponding From impls could be used to convert a plain string to an error
type. Rust 1.7 added support for conversion from &str/String to
Box<Error>, so this gotcha and later references to it can now be removed.

…nor gather flags for untracked content.

(Includes a regression test, which needed to go into `compile-fail/`
due to weaknesses when combining `#[deny(warnings)]` with
`tcx.sess.span_warn(..)`)

(updated with review feedback from arielb1.)

Rewrote "How Safe and Unsafe Interact" Nomicon chapter.

The previous version of the chapter covered a lot of ground, but was a little meandering and hard to follow at times. This draft is intended to be clearer and more direct, while still providing the same information as the previous version.

r? @steveklabnik

…umeGomez

run rustfmt on librustc_lint folder

Fix wrong statement in compare_exchange doc

The documentation for `core::sync::atomic::AtomicSomething::compare_exchange` contains a wrong, or imprecise, statement about the return value. It goes:

The return value is a result indicating whether the new value was written and containing
the previous value. On success this value is guaranteed to be equal to `new`.

In the second sentence, `this value` is gramatically understood as referring to `return value` from the first sentence. Due to how CAS works, the returned value is always what was in the atomic variable _before_ the operation occurred, not what was written into it during the operation. Hence, the fixed doc should say:

The return value is a result indicating whether the new value was written and containing
the previous value. On success this value is guaranteed to be equal to `current`.

This version is confirmed by the runnable examples in variants of `AtomicSomething`, e.g.

    assert_eq!(some_bool.compare_exchange(true, false, Ordering::Acquire, Ordering::Relaxed),
    Ok(true));

where the returned value is `Ok(current)`. This PR fixes all occurrences of this bug I could find.

An alternative solution would be to modify the second sentence so that it refers to the value _written_ into the Atomic rather than what was there before, in which case it would be correct. Example alternative formulation:

On success the value written into the `bool`/`usize`/`whatever` is guaranteed to be equal to `new`.

r? @steveklabnik

run rustfmt on map.rs in libcollections/btree folder

…n, r=nrc

Refactor away the prelude injection fold

Instead, just inject `#[prelude_import] use [core|std]::prelude::v1::*;` at the crate root while injecting `extern crate [core|std];` and process `#[no_implicit_prelude]` attributes in `resolve`.

r? @nrc

Fix issue rust-lang#34101

Fix issue rust-lang#34101: do not track subcontent of type with dtor nor gather flags for untracked content.

(Includes a regression test, which needed to go into `compile-fail/`
due to weaknesses when combining `#[deny(warnings)]` with
`tcx.sess.span_warn(..)`)

…veklabnik

Remove a gotcha from book/error-handling.md

The book's "Error handling with `Box<Error>`" section talks about `Box<Error>`. In the actual example `Box<Error + Send + Sync>` is used instead so that the corresponding From impls could be used to convert a plain string to an error type. Rust 1.7 added support for conversion from `&str`/`String` to
`Box<Error>`, so this gotcha and later references to it can now be removed.

r? @steveklabnik

Add explanations for E0503 and E0508.

(cannot use `..` because it was mutably borrowed, cannot move out of type `..`, a non-copy fixed-size array)

Part of rust-lang#32777.

…=nikomatsakis

Test case for borrowk ICE rust-lang#25579

r? @nikomatsakis

Fixes rust-lang#25579

docs: simplify wording

It took me more then a moment to decipher "with no non-`'static`" thing :)

"`'static` type" should say the same thing more clearly.

r? @steveklabnik