Add peer_addr function to UdpSocket

Fixes #59104

This is my first pull request to Rust, so opening early for some feedback.

My biggest question is: where do I add tests?

Any comments very much appreciated!

FreeBSD 10.x is EOL, in FreeBSD 11 and later, ss_sp is actually a void*

…d* [1]

dragonflybsd still uses c_char [2]

[1] https://svnweb.freebsd.org/base/releng/11.2/sys/sys/signal.h?revision=334459&view=markup#l438
[2] https://github.com/DragonFlyBSD/DragonFlyBSD/blob/master/sys/sys/signal.h#L339

When encountering `||{}()`, suggest the likely intended `(||{})()`

Fix #55851.

Refactor tools/build-mainfest

I saw some duplication in https://github.com/rust-lang/rust/pull/58990 and got an itch... Will likely need to be rebased when that lands. Hopefully the PR should have zero semantic changes...

r? @alexcrichton

Recover from missing comma between enum variants and from bad `pub` kw

Fix #56579. Fix #56473.

Point at coercion reason for `if` expressions without else clause if caused by return type

```
error[E0317]: if may be missing an else clause
  --> $DIR/if-without-else-as-fn-expr.rs:2:5
   |
LL |   fn foo(bar: usize) -> usize {
   |                         ----- found `usize` because of this return type
LL | /     if bar % 5 == 0 {
LL | |         return 3;
LL | |     }
   | |_____^ expected (), found usize
   |
   = note: expected type `()`
              found type `usize`
   = note: `if` expressions without `else` must evaluate to `()`
```

Fix #25228.

hygiene: Fix identifier comparison in impl overlap check

Fixes https://github.com/rust-lang/rust/issues/58942

dragonflybsd still uses c_char [2]

[1] https://svnweb.freebsd.org/base/releng/11.2/sys/sys/signal.h?revision=334459&view=markup#l438
[2] https://github.com/DragonFlyBSD/DragonFlyBSD/blob/master/sys/sys/signal.h#L339

Add provided methods `Seek::{stream_len, stream_position}`

This adds two new, provided methods to the `io::Seek` trait:
- `fn stream_len(&mut self) -> Result<u64>`
- `fn stream_position(&mut self) -> Result<u64>`

Both are added for convenience and to improve readability in user code. Reading `file.stream_len()` is much better than to manually seek two or three times. Similarly, `file.stream_position()` is much more clear than `file.seek(SeekFrom::Current(0))`.

You can find prior discussions [in this internals thread](https://internals.rust-lang.org/t/pre-rfc-idea-extend-io-seek-with-convenience-methods-with-e-g-stream-len/9262). I think I addressed all concerns in that thread.

I already wrote three RFCs to add a small new API to libstd but I noticed that many public changes to libstd happen without an RFC. So I figured I can try opening a PR directly without going through RFCs first. After all, we do have rfcbot here too. If you think this change is too big to merge without an RFC, I can still close this PR and write an RFC.

Add default keyword handling in rustdoc

Fixes #58898.

r? @QuietMisdreavus

Add new test case for possible bug in BufReader

When reading a large chunk from a BufReader, if all the bytes from the buffer have been already consumed, the internal buffer is bypassed entirely. However, it is not invalidated, and it's possible to access its contents using the `seek_relative` method, because it tries to reuse the existing buffer.

Fixes for the generator transform

* Moves cleanup annotations in pretty printed MIR so that they can be tested
* Correctly determines which drops are in cleanup blocks when elaborating generator drops
* Use the correct state for poisoning a generator

Closes #58892

Rework how bootstrap tools are built

This makes bootstrap tools buildable and testable in stage 0 with the downloaded bootstrap compiler, futhermore, it makes it such that they cannot be built in any other stage.

Notably, this will also mean that compiletest may need to wait a cycle before it can use changes to `libtest`, as it no longer depends on the in-tree libtest.

Introduce assembly tests suite

The change introduces a new test suite - **Assembly** tests. The motivation behind this is an ability to perform end-to-end codegen testing with LLVM backend. Turned out, NVPTX backend sometimes missing common Rust features (`i128` and libcalls in the past, and still full atomics support) due to different reasons.

Prior to this change, basic NVPTX assembly tests were implemented within `run-make` suite. Now, it's easier to write additional and maintain existing tests for the target.

cc @gnzlbg @peterhj
cc @EddyB I adjusted mangling scheme expectation, so there is no need to change the tests for #57967

Keep last redundant linker flag, not first

When a library (L1) is passed to the linker multiple times, this is sometimes purposeful: there might be several other libraries in the linker command (L2 and L3) that all depend on L1.  You'd end up with a (simplified) linker command that looks like:

```
-l2 -l1 -l3 -l1
```

With the previous behavior, when rustc encountered a redundant library, it would keep the first instance, and remove the later ones, resulting in:

```
-l2 -l1 -l3
```

This can cause a linker error, because on some platforms (e.g. Linux), the linker will only include symbols from L1 that are needed *at the point it's referenced in the command line*.  So if L3 depends on additional symbols from L1, which aren't needed by L2, the linker won't know to include them, and you'll end up with "undefined symbols" errors.

A better behavior is to keep the *last* instance of the library:

```
-l2 -l3 -l1
```

This ensures that all "downstream" libraries have been included in the linker command before the "upstream" library is referenced.

Fixes rust-lang#47989

Rollup of 5 pull requests (all of which changes `src/ci/docker`)

Successful merges:

 - #58986 ([CI] Update binutils for powerpc64 and powerpc64le)
 - #59038 (Track embedded-book in the toolstate)
 - #59055 (CI: Set job names.)
 - #59253 (Calculate Docker cache hash precisely from Dockerfile's dependencies)
 - #59257 (Update CI configuration for building Redox libraries)

Failed merges:

r? @ghost

Update CI configuration for building Redox libraries

This fixes https://github.com/rust-lang/rust/issues/59254

Calculate Docker cache hash precisely from Dockerfile's dependencies

#58549 changed the Docker cache calculation to include every file under `src/ci/docker`, so that when files under `dist-x86_64-linux` is changed, its dependent image `dist-i686-linux` will also be rebuilt.

However, this ultraconservative solution caused the `dist-i686-linux` to be rebuilt every time an irrelevant Dockerfile (e.g. the PowerPC ones) is changed, which increases the building time beyond 3 hours and forcing a spurious but expected failure.

This commit instead parses the Dockerfile itself and look for the actual dependencies. The scripts needs to be copied into the Docker image, which must be done with the COPY command, so we just need to find all lines with a COPY command and add the source file into the hash calculator.

Note: this script only handles single-lined COPY command in the form `COPY src1 src2 src3 dst`, since these are the only variant used inside this repository.

CI: Set job names.

This should make it easier to identify what each job is doing when looking at the Travis or Appveyor UI.

- Set `name` for each job in Travis.
- Move `CI_JOB_NAME` to the front in Appveyor so that it appears first in the UI.

Track embedded-book in the toolstate

The embedded book was tested in the tools job but the test result was never published. This PR adds maintainer information of embedded-book. This PR also requires the next update to embedded-book to pass the all tests, currently its state is test-fail.

rust-lang-nursery/rust-toolstate#10 should be merged before this PR.

[CI] Update binutils for powerpc64 and powerpc64le

Cargo powerpc64 and powerpc64le are seeing `SIGILL` crashes in openssl,
which was found to be a linking problem, fixed by newer binutils. See
<https://github.com/rust-lang/rust/issues/57345#issuecomment-462094555>

For powerpc64 we're using crosstool-ng, which doesn't offer a newer
binutils version, but we can just compile it separately. On powerpc64le
we're already building binutils. Both are now updated to binutils 2.32.

Closes rust-lang/cargo#6320
Closes rust-lang/rust#57345
Closes rust-lang/rustup.rs#1620

r? @alexcrichton

Move libtest out of rust-lang/rust

This is a first step towards a number of goals explained in this internals post: https://internals.rust-lang.org/t/a-path-forward-towards-re-usable-libtest-functionality-custom-test-frameworks-and-a-stable-bench-macro

This PR does not fully remove libtest from rust-lang/rust, we keep a shim that imports and re-exports the external libtest, and adds the proc_macro dependency, etc.

r? @alexcrichton

cc @djrenren @petrochenkov

Rollup of 11 pull requests

Successful merges:

 - #56348 (Add todo!() macro)
 - #57729 (extra testing of how NLL handles wildcard type `_`)
 - #57847 (dbg!() without parameters)
 - #58778 (Implement ExactSizeIterator for ToLowercase and ToUppercase)
 - #58812 (Clarify distinction between floor() and trunc())
 - #58939 (Fix a tiny error in documentation of std::pin.)
 - #59116 (Be more discerning on when to attempt suggesting a comma in a macro invocation)
 - #59252 (add self to mailmap)
 - #59275 (Replaced self-reflective explicit types with clearer `Self` or `Self::…` in stdlib docs)
 - #59280 (Stabilize refcell_map_split feature)
 - #59290 (Run branch cleanup after copy prop)

Failed merges:

r? @ghost

Run branch cleanup after copy prop

This is preliminary work for https://github.com/rust-lang/rust/pull/59288#issuecomment-474277172 which gets rid of `if` in the HIR.

cc @rust-lang/wg-mir-opt 	@Centril

Stabilize refcell_map_split feature

Closes #51476.

Replaced self-reflective explicit types with clearer `Self` or `Self::…` in stdlib docs

Many docs examples use explicit types instead of the semantically more clear `Self`/`Self::…` aliases.

By using the latter it's clear that the value's type depends on either `Self`, or an associated type of `Self`, instead of some constant type. It's also more consistent (and I'd argue correct), as the current docs aren't really consistent in this, as can be seen from the diff.

This is a best effort PR, as I was basically going through the docs manually, looking for offending examples. I'm sure I missed a few. Gotta start somewhere.

add self to mailmap

Be more discerning on when to attempt suggesting a comma in a macro invocation

Fix #58796.

Fix a tiny error in documentation of std::pin.

`new_unmoved` must be `mut` for passing to `std::mem::swap`.

Clarify distinction between floor() and trunc()

`floor()` rounds towards `-INF`, `trunc()` rounds towards 0.
This PR clarifies this in the examples.

Implement ExactSizeIterator for ToLowercase and ToUppercase

dbg!() without parameters

Fixes #57845.

Rollup merge of #57729 - pnkfelix:issue-55748-pat-types-are-constraints-on-bindings-too, r=nikomatsakis

extra testing of how NLL handles wildcard type `_`

test that wildcard type `_` is not duplicated by `type Foo<X> = (X, X);` and potentially instantiated at different types when used in type ascriptions in let bindings.

(NLL's handling of this for the type ascription *expression form* is currently broken, or at least differs from what AST-borrowck does. I'll file a separate bug about that. Its not something critical to address since that expression is guarded by `#![feature(type_ascription)]`.)

cc #55748

Add todo!() macro

The primary use-case of `todo!()` macro is to be a much easier to type
alternative to `unimplemented!()` macro.

EDIT: hide unpopular proposal about re-purposing unimplemented

<details>
However, instead of just replacing `unimplemented!()`, it gives it a
more nuanced meaning: a thing which is intentionally left
unimplemented and which should not be called at runtime. Usually,
you'd like to prevent such cases statically, but sometimes you, for
example, have to implement a trait only some methods of which are
applicable. There are examples in the wild of code doing this thing,
and in this case, the current message of `unimplemented`, "not *yet*
implemented" is slightly misleading.

With the addition of TODO, you have three nuanced choices for a
`!`-returning macro (in addition to a good-old panic we all love):

  * todo!()
  * unreachable!()
  * unimplemented!()

Here's a rough guideline what each one means:

- `todo`: use it during development, as a "hole" or placeholder. It
  might be a good idea to add a pre-commit hook which checks that
  `todo` is not accidentally committed.

- `unreachable!()`: use it when your code can statically guarantee
  that some situation can not happen. If you use a library and hit
  `unreachable!()` in the library's code, it's definitely a bug in the
  library. It's OK to have `unreachable!()` in the code base,
  although, if possible, it's better to replace it with
  compiler-verified exhaustive checks.

- `unimplemented!()`: use it when the type checker forces you to
  handle some situation, but there's a contract that a callee must not
  actually call the code. If you use a library and hit
  `unimplemented!()`, it's probably a bug in your code, though
  it *could* be a bug in the library (or library docs) as well. It is
  ok-ish to see an `unimplemented!()` in real code, but it usually
  signifies a clunky, eyebrow-rising API.
</details>