The Rust version number is currently embedded in bootstrap's source
code, which makes it hard to update it automatically or access it
outside of ./x.py (as you'd have to parse the source code).

This commit moves the version number to a standalone plaintext file,
which makes accessing or updating it trivial.

Improve E0118

- Changes the "base type" terminology to "nominal type" (according to the [reference](https://doc.rust-lang.org/stable/reference/items/implementations.html#inherent-implementations)).
- Suggests removing a reference, if one is present on the type.
- Clarify what is meant by a "nominal type".

closes #69392

This is my first not-entirely-trivial PR, so please let me know if I missed anything or if something could be improved. Though I probably won't be able to fix anything in the upcoming week.

Rollup of 16 pull requests

Successful merges:

 - #75026 (Add array_windows fn)
 - #76642 (Do not lint ignored private doc tests)
 - #76719 (Change error message for ty param in const)
 - #76721 (Use intra-doc links in `core::mem`)
 - #76728 (Add a comment why `extern crate` is necessary for rustdoc)
 - #76735 (Remove unnecessary `clone()`s in bootstrap)
 - #76741 (Avoid printing dry run timings)
 - #76747 (Add missing code examples in libcore)
 - #76756 (fix a couple of stylistic clippy warnings)
 - #76758 ([fuchsia] Propagate the userspace UTC clock)
 - #76759 (Fix stabilization marker for future_readiness_fns)
 - #76760 (don't lazily evaluate some trivial values for Option::None replacements (clippy::unnecessary_lazy_evaluations))
 - #76764 (Update books)
 - #76775 (Strip a single leading tab when rendering dataflow diffs)
 - #76778 (Simplify iter fuse struct doc)
 - #76794 (Make graphviz font configurable)

Failed merges:

r? `@ghost`

Make graphviz font configurable

Alternative to PR #76776.

To change the graphviz output to use an alternative `fontname` value,
add a command line option like: `rustc --graphviz-font=monospace`.

r? @ecstatic-morse

Simplify iter fuse struct doc

Strip a single leading tab when rendering dataflow diffs

The `fmt_diff_with` formatter uses a tab to separate additions from subtractions. Strip it when rendering those diffs on separate lines.

r? @Mark-Simulacrum (since you're speedy)

Update books

## nomicon

1 commits in 25854752549d44d76fbd7650e17cb4f167a0b8fb..6e57e64501f61873ab80cb78a07180a22751a5d6
2020-08-19 16:41:48 -0400 to 2020-09-14 11:40:23 -0400
- Fix API change to alloc::Global::grow. (rust-lang-nursery/nomicon#236)

## reference

3 commits in 25391dba46262f882fa846beefaff54a966a8fa5..56a13c082ee90736c08d6abdcd90462517b703d3
2020-09-02 07:22:55 -0700 to 2020-09-14 23:20:16 -0700
- Update the description of staticlib (rust-lang-nursery/reference#884)
- Rust 1.46 now allows more features in const fn (rust-lang-nursery/reference#883)
- Document the enum changes in RFC 2195 (rust-lang-nursery/reference#879)

## book

1 commits in e5ed97128302d5fa45dbac0e64426bc7649a558c..cb28dee95e5e50b793e6ba9291c5d1568d3ad72e
2020-08-31 12:53:40 -0500 to 2020-09-09 10:06:00 -0500
- Fixed the error message of invalid array element access in ch03.2 (rust-lang/book#2446)

don't lazily evaluate some trivial values for Option::None replacements (clippy::unnecessary_lazy_evaluations)

Fix stabilization marker for future_readiness_fns

Updated the rustc version in which this will be stabilized from `1.47.0 -> 1.48.0`. Fixes https://github.com/rust-lang/rust/pull/74328#issuecomment-692133125. Ref #70921.

r? @Dylan-DPC

[fuchsia] Propagate the userspace UTC clock

On Fuchsia, spawning a subprocess does not automatically
clone all of the parent process' capabilities. UTC time on
Fuchsia is managed by a top-level userspace clock capability
that is cloned and passed to subprocesses.

This change ensures that any Rust subprocess gets access to the
UTC clock, if the parent had access to it. This is critical for
tests, which on Fuchsia, use panic=abort and spawn subprocesses
per test.

fix a couple of stylistic clippy warnings

namely:

clippy::redundant_pattern_matching
clippy::redundant_pattern
clippy::search_is_some
clippy::filter_next
clippy::into_iter_on_ref
clippy::clone_on_copy
clippy::needless_return

Add missing code examples in libcore

Avoid printing dry run timings

This avoids a wall of text on CI with 0.000 as the likely time.

r? @alexcrichton

Remove unnecessary `clone()`s in bootstrap

The performance difference is negligible, but it makes me feel better.

r? @Mark-Simulacrum

Add a comment why `extern crate` is necessary for rustdoc

r? @ehuss

From https://github.com/rust-lang/rust/pull/74293#discussion_r488335500.

Use intra-doc links in `core::mem`

Part of #75080.

Last one for now!

---

@rustbot modify labels: A-intra-doc-links T-doc

Change error message for ty param in const

This PR introduces the following changes:

* Change error message for type param in a const expression when using
`min_const_generics`
* Change `ParamInNonTrivialAnonConst` to contain an extra `bool` used for
distinguishing whether the passed-in symbol is a type or a value.

Fixes #76701

Do not lint ignored private doc tests

Fixes #76457.

r? @ehuss

Add array_windows fn

This mimicks the functionality added by array_chunks, and implements a const-generic form of
`windows`. It makes egregious use of `unsafe`, but by necessity because the array must be
re-interpreted as a slice of arrays, and unlike array_chunks this cannot be done by casting the
original array once, since each time the index is advanced it needs to move one element, not
`N`.

I'm planning on adding more tests, but this should be good enough as a premise for the functionality.
Notably: should there be more functions overwritten for the iterator implementation/in general?

~~I've marked the issue as #74985 as there is no corresponding exact issue for `array_windows`, but it's based of off `array_chunks`.~~

Edit: See Issue #75027 created by @lcnr for tracking issue

~~Do not merge until I add more tests, please.~~

r? @lcnr

Overrides the debugging_opts.graphviz_font setting.

Add aarch64-unknown-linux-musl host builds

This adds aarch64-unknown-linux-musl to the hosts list and adds the build to the dist-arm-linux builder as `@Mark-Simulacrum` suggested to me in Zulip. `@jyn514` requested to be mentioned 😄

I had to update the config for crosstool-ng as it had a prompt about the glibc version.

I ran `src/ci/docker/run.sh dist-arm-linux` to test it.

```
Build completed successfully in 1:31:50
Compile requests              8180
Compile requests executed     8135
Cache hits                     287
Cache misses                  7848
Cache timeouts                   0
Cache read errors                0
Forced recaches                  0
Cache write errors               0
Compilation failures             0
Cache errors                     0
Non-cacheable compilations       0
Non-cacheable calls             36
Non-compilation calls            9
Unsupported compiler calls       0
Average cache write          0.000 s
Average cache read miss      6.389 s
Average cache read hit       0.000 s
Cache location             Local disk: "/sccache"
Cache size                     202 MiB
Max cache size                  10 GiB
== clock drift check ==
  local time: Sun Sep  6 19:30:17 UTC 2020
  network time: Sun, 06 Sep 2020 19:30:17 GMT
== end clock drift check ==
```

Only errors were in miri due to struct fields being private (already been reported [here](https://github.com/rust-lang/rust/issues/76337))

Edit: Maybe it is helpful if I add that it is a working compiler
```sh
/rust-nightly-aarch64-unknown-linux-musl # ash install.sh
install: creating uninstall script at /usr/local/lib/rustlib/uninstall.sh
install: installing component 'rustc'
install: installing component 'cargo'
install: installing component 'rls-preview'
install: installing component 'rust-analyzer-preview'
install: installing component 'clippy-preview'
install: installing component 'rustfmt-preview'
install: installing component 'llvm-tools-preview'
install: installing component 'rust-analysis-aarch64-unknown-linux-musl'
install: installing component 'rust-std-aarch64-unknown-linux-musl'
install: WARNING: failed to run ldconfig. this may happen when not installing as root. run with --verbose to see the error

    Rust is ready to roll.

/ # cat test.rs
fn main() { println!("hello world"); }
/ # rustc test.rs
/ # ./test
hello world
 # file test
test: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), statically linked, not stripped
```

Alternative to PR ##76776.

To change the graphviz output to use an alternative `fontname` value,
add a command line option like: `rustc --graphviz-font=monospace`.

Updated issue to #75027

Update to rm oob access

And hopefully fix docs as well

Fixed naming conflict in test

Fix test which used 1-indexing

Nth starts from 0, woops

Fix a bunch of off by 1 errors

See https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=757b311987e3fae1ca47122969acda5a

Add even more off by 1 errors

And also write `next` and `next_back` in terms of `nth` and `nth_back`.

Run fmt

Fix forgetting to change fn name in test

add nth_back test & document unsafe

Remove as_ref().unwrap()
Documented occurrences of unsafe, noting what invariants are maintained

Rollup of 10 pull requests

Successful merges:

 - #76669 (Prefer asm! over llvm_asm! in core)
 - #76675 (Small improvements to asm documentation)
 - #76681 (remove orphaned files)
 - #76694 (Introduce a PartitioningCx struct)
 - #76695 (fix syntax error in suggesting generic constraint in trait parameter)
 - #76699 (improve const infer error)
 - #76707 (Simplify iter flatten struct doc)
 - #76710 (⬆ rust-analyzer)
 - #76714 (Small docs improvements)
 - #76717 (Fix generating rustc docs with non-default lib directory.)

Failed merges:

r? `@ghost`

The performance difference is negligible, but it makes me feel better.

Note that this does not remove some clones in `config`, because it would
require changing the logic around (and performance doesn't matter
for bootstrap).

Fix generating rustc docs with non-default lib directory.

If `libdir` is set in `config.toml`, then the tool to generate the rustc docs was unable to run `rustc` because it could not find the shared libraries. The solution is to set the dylib search path to include the libdir.

I changed the API of `add_rustc_lib_path` to take `Command` instead of `Cargo` to try to share the code in several places. This is how it worked before https://github.com/rust-lang/rust/pull/64316, and I think this still retains the spirit of that change.

Fixes #76702

Small docs improvements

@rustbot modify labels: T-doc T-compiler

⬆ rust-analyzer

r? @ghost

Simplify iter flatten struct doc

improve const infer error

cc #72328

reduces it from
```
error[E0282]: type annotations needed
  --> src/main.rs:17:5
   |
17 |     Foo.bar().bar().bar().bar().baz();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: unable to infer the value of a const parameter
```
to
```
error[E0282]: type annotations needed
  --> $DIR/method-chain.rs:21:33
   |
LL |     Foo.bar().bar().bar().bar().baz();
   |                                 ^^^
   |
   = note: cannot infer the value of the const parameter `N`
```

r? @varkor

fix syntax error in suggesting generic constraint in trait parameter

suggest `where T: Foo` for the first bound on a trait, then suggest
`, T: Foo` when the suggested bound would add to an existing set of
`where` clauses. `where T: Foo` may be the first bound if `T` has a
default, because we'd rather suggest
```
trait A<T=()> where T: Copy
```
than
```
trait A<T: Copy=()>
```
for legibility reasons.

the test case i added here is derived from [this reproduction](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=0bf3ace9f2a183d0bdbd748c6b8e3971):
```
struct B<T: Copy> {
    t: T
}

trait A<T = ()> {
    fn returns_constrained_type(&self, t: T) -> B<T> {
        B { t }
    }
}
```
where the suggested fix,
```
trait A<T = ()>, T: Copy { ... }
```
is in fact invalid syntax!

i also found an error in the existing suggestion for `trait Base<T = String>: Super<T>` where rustc would suggest `trait Base<T = String>: Super<T>, T: Copy`, but `T: Copy` is the first of the trait's `where` clauses and should be `where T: Copy` as well. the test for that suggestion expects invalid syntax, and has been revised to a compiler-pleasing `trait Base<T = String>: Super<T> where T: Copy`.

judging by https://github.com/rust-lang/rust/pull/70009 i'll.. cc @estebank ?

Introduce a PartitioningCx struct

This contains all the data used by the partitioning algorithm and allows that data to be used at each stage of the partitioning. This is useful for other approaches to partitioning which may want different pieces of the data available at each step.

cc @rust-lang/wg-incr-comp

remove orphaned files

Should been part of https://github.com/rust-lang/rust/pull/74163

Small improvements to asm documentation

Save people from searching and reading tons of comments in tracking issues.

Prefer asm! over llvm_asm! in core

Replace llvm_asm! with asm! in core.

x86 asm compare (in somecases I replaced generic type with String).
* https://rust.godbolt.org/z/59eEMv
* https://rust.godbolt.org/z/v78s6q
* https://rust.godbolt.org/z/7qYY41

Co-authored-by: NAmanieu <amanieu@gmail.com>

Rollup of 10 pull requests

Successful merges:

 - #76056 (Add more info for Vec Drain doc)
 - #76062 (Vec slice example fix style and show type elision)
 - #76262 (Use inline(never) instead of cold)
 - #76335 (Make all methods of `Duration` unstably const)
 - #76366 (Add Arith Tests in Library)
 - #76369 (Move Various str tests in library)
 - #76534 (Add doc comments for From impls)
 - #76622 (Update bootstrap readme)
 - #76641 (Some cleanup changes and commenting)
 - #76662 (Fix liballoc test suite for Miri)

Failed merges:

r? `@ghost`

Fix liballoc test suite for Miri

Mostly, fix the regression introduced by https://github.com/rust-lang/rust/pull/75207 that caused slices (i.e., references) to be created to invalid memory or memory that has aliasing pointers that we want to keep valid. @dylni  this changes the type of `check_range` to only require the length, not the full reference to the slice, which indeed is all the information this function requires.

Also reduce the size of a test introduced in https://github.com/rust-lang/rust/pull/70793 to make it not take 3 minutes in Miri.

This makes https://github.com/RalfJung/miri-test-libstd work again.

Some cleanup changes and commenting

r? @nikomatsakis
Cc @EddyB

Update bootstrap readme

- Reflect changes in x.py defaults
- Remove recommendation to use nightly for incremental; it works fine on
beta
- Remove note that incremental chooses stage 1 by default; stage 1 is
already the default
- Update Discord -> Zulip

r? @Mark-Simulacrum