Also:
1. stop eagerly coercing from `[T, ..n]` to `[T]` only do so if requested.
2. permit error to be interact more freely.

Fixes #17178.

have to take the transformed self type into account, and allow for coercion between
the receiver and the actual type declared on the impl.

Finishes the job of #17286.

Now the stability lint will successfully detect patterns such as:
```
first_macro!(second_macro!(deprecated_function()));
```
```
macro_rules! foo (
    ($e: expr) => (bar!($e))
)
foo!(deprected_function());
```
and
```
println!("{}", deprecated_function());
```
even with more levels of nesting, such as
```
println!("{}", foo!(bar!(deprecated_function())));
```

This was run into while attempting to integrate rust with bitbake's build system. I expect it's caused by some other environment variables being set to gcc but didn't track down the exact cause myself.

This is an almost-done draft of a guide on crates and modules. This is a hard guide to get right, I had to remove a chunk of the Guide because it was confusing.

I've also pushed up https://github.com/steveklabnik/phrases which has matching code. Whenever we finish this guide, I think it'd be good to have a sample crate like this in the rust-lang org for people to compare against. The hardest part of a guide like this is that it depends on multiple files being correct, and being able to point to a repository would be very helpful.

Things yet to do:

1. external crates via cargo
2. documentation

I'm super open to still revising this if it's still confusing. There's been a lot of Reddit discussion about the module system, and I tried to incorporate those posts and the comments into this.

/cc @huonw 

Closes #17185.

Noticed a type while reading through the intro

Fixes #17340

This is a large spring-cleaning commit now that the 0.12.0 release has passed removing an amount of deprecated functionality. This removes a number of deprecated crates (all still available as cargo packages in the rust-lang organization) as well as a slew of deprecated functions. All `#[crate_id]` support has also been removed.

I tried to avoid anything that was recently deprecated, but I may have missed something! The major pain points of this commit is the fact that rustc/syntax have `#[allow(deprecated)]`, but I've removed that annotation so moving forward they should be cleaned up as we go.

Closes #9987.

Closes #9987.

This optimizes `read` for the case in which the number of bytes
requested is larger than the internal buffer. Note that the first
comparison occurs again right afterwards and should thus be free. The
second comparison occurs only in the cold branch.

This optimizes `read` for the case in which the number of bytes
requested is larger than the internal buffer. Note that the first
comparison occurs again right afterwards and should thus be free. The
second comparison occurs only in the cold branch.

Fix for issue #18091 

The problem seems to be that `ast_util::int_ty_to_string` takes unsigned number, and no one adds `-` to result string. I've fixed it by putting `-` before result string using `format!`.

I've also added `test_signed_int_to_string()` to check if implementation is valid.

Fixes #18107 

r? @EddyB

While no real rvalue of an unsized type can exist, a diverging function
can still "return" a value of such a type, which causes an ICE.

Fixes #18107.

Spring cleaning is here! In the Fall! This commit removes quite a large amount
of deprecated functionality from the standard libraries. I tried to ensure that
only old deprecated functionality was removed.

This is removing lots and lots of deprecated features, so this is a breaking
change. Please consult the deprecation messages of the deleted code to see how
to migrate code forward if it still needs migration.

[breaking-change]

All of these crates have been deprecated for some time and properly live in the
rust-lang organization as cargo-based crates.

To update your code, depend on the rust-lang/foo repository via cargo.

[breaking-change]

The explanation of fold talks about three elements that should be summed, but it uses different values in the provided code.

Fixes issue #18090

let mut value = mutex.lock();
warning: variable does not need to be mutable

Check for borrow of local variable introduced within static block.

(Rather than ICE on it.)

Fix #18118.

Use a match expression directly in the println statement, instead of creating a second variable.  It seems weird that the current guide.md complains about creating an extra variable, when the same feature could be demonstrated without creating the extra variable.

Closes #16939

When translating the unboxing shim, account for the fact that the shim translation has already performed the necessary unboxing of input types and values when forwarding to the shimmed function.  This prevents ICEing or generating incorrect code.

Closes #16739

The explanation of fold talks about three elements that should be summed, but it uses different values in the provided code.