Guide: testing
Library changes for RFC #43
Add two helper functions for dealing with OwnedPtr paths
Implement RFC #43

Remove the ability of the borrow checker to determine that repeated
dereferences of a Box<T> refer to the same memory object. This will
usually require one of two workarounds:

1) The interior of a Box<T> will sometimes need to be moved / borrowed
into a temporary before moving / borrowing individual derived paths.

2) A `ref x` pattern will have to be replaced with a `box ref x`
pattern.

Fixes #16094.

[breaking-change]
Add a new test for borrow checker Box<T> behavior
Add comment about speed in FAQ.

Fixes #11174.
Guide: pointers

Not the pointer guide, but the guide section on pointers.

Adding a section about patterns for after this, as well.
doc: fix typos in std::num::Int
Stop using the Show impl for ast::Name in our symbols

When generating a unique symbol for things like closures or glue_drop,
we call token::gensym() to create a crate-unique Name. Recently, Name
changed its Show impl so it no longer prints as a number. This caused
symbols like glue_drop:1542 to become glue_drop:"glue_drop"(1542), or in
mangled form, glue_drop.$x22glue_drop$x22$LP$1542$RP$.
Be more consistent with "Hello, world!"
libserialize: add `error()` to `Decoder`

A quick and dirty fix for #15036 until we get serious decoder reform.

Right now it is impossible for a Decodable to signal a decode error,
for example if it has only finitely many allowed values, is a string
which must be encoded a certain way, needs a valid checksum, etc. For
example in the libuuid implementation of Decodable an Option is
unwrapped, meaning that a decode of a malformed UUID will cause the
task to fail.

Since this adds a method to the `Decoder` trait, all users will need
to update their implementations to add it. The strategy used for the
current implementations for JSON and EBML is to add a new entry to
the error enum `ApplicationError(String)` which stores the string
provided to `.error()`.

[breaking-change]
libuuid: use `Decoder::error()` rather than failing on bad decode
auto merge of #16130 : apoelstra/rust/decode-error, r=alexcrichton

A quick and dirty fix for #15036 until we get serious decoder reform.

Right now it is impossible for a `Decodable` to signal a decode error, for example if it has only finitely many allowed values, is a string which must be encoded a certain way, needs a valid checksum, etc. For example in the `libuuid` implementation of `Decodable` an `Option` is unwrapped, meaning that a decode of a malformed UUID will cause the task to fail.
rustdoc: Use --crate-name with --test

This ensures that the name of the crate is set from the command line for tests
so the auto-injection of `extern crate <name>` in doc tests works correctly.
auto merge of #16152 : tshepang/rust/patch-1, r=alexcrichton
Add is_unique(), try_unwrap(), get_mut() to alloc::rc

Add a few new free functions to alloc::rc for manipulating
uniquely-owned Rc values. is_unique() can be used to test if the Rc is
uniquely-owned, try_unwrap() can remove the value from a uniquely-owned
Rc, and get_mut() can return a &mut for a uniquely-owned Rc.

These are all free functions, because smart pointers should avoid having
methods when possible. They can't be static methods because UFCS will
remove that distinction. I think we should probably change downgrade()
and make_unique() into free functions as well, but that's out of scope.
auto merge of #16101 : kballard/rust/rc_unique_ownership, r=aturon

Add a few new free functions to alloc::rc for manipulating
uniquely-owned Rc values. is_unique() can be used to test if the Rc is
uniquely-owned, try_unwrap() can remove the value from a uniquely-owned
Rc, and get_mut() can return a &mut for a uniquely-owned Rc.

These are all free functions, because smart pointers should avoid having
methods when possible. They can't be static methods because UFCS will
remove that distinction. I think we should probably change downgrade()
and make_unique() into free functions as well, but that's out of scope.
auto merge of #16153 : kballard/rust/fix_gensym_symbols, r=luqmana

When generating a unique symbol for things like closures or glue_drop,
we call token::gensym() to create a crate-unique Name. Recently, Name
changed its Show impl so it no longer prints as a number. This caused
symbols like glue_drop:1542 to become glue_drop:"glue_drop"(1542), or in
mangled form, glue_drop.$x22glue_drop$x22$LP$1542$RP$.
auto merge of #16157 : alexcrichton/rust/rustdoc-tests, r=huonw

This ensures that the name of the crate is set from the command line for tests
so the auto-injection of `extern crate <name>` in doc tests works correctly.
librustc: Forbid pattern bindings after `@`s, for memory safety.

This is an alternative to upgrading the way rvalues are handled in the
borrow check. Making rvalues handled more like lvalues in the borrow
check caused numerous problems related to double mutable borrows and
rvalue scopes. Rather than come up with more borrow check rules to try
to solve these problems, I decided to just forbid pattern bindings after
`@`. This affected fewer than 10 lines of code in the compiler and
libraries.

This breaks code like:

    match x {
        y @ z => { ... }
    }

    match a {
        b @ Some(c) => { ... }
    }

Change this code to use nested `match` or `let` expressions. For
example:

    match x {
        y => {
            let z = y;
            ...
        }
    }

    match a {
        Some(c) => {
            let b = Some(c);
            ...
        }
    }

Closes #14587.

[breaking-change]