Update miri

Make rustc::middle::region::Scope's fields public

This PR makes the following changes to `rustc::middle::region::Scope`:

- [x] Makes `region::Scope`'s fields public
- [x] Removes the `impl Scope` block with constructors (as per [this comment](https://github.com/rust-lang/rust/pull/54032#discussion_r216618208))
- [x] Updates call sites throughout the compiler

Closes #54122.

miri engine: keep around some information for dead allocations

We use it to test if a dangling ptr is aligned and non-NULL. This makes some code pass that should pass (writing a ZST to a properly aligned dangling pointer), and makes some code fail that should fail (writing a ZST to a pointer obtained via pointer arithmetic from a real location, but ouf-of-bounds -- that pointer could be NULL, so we cannot allow writing to it).

CTFE does not allow these operations; tests are added to miri with https://github.com/solson/miri/pull/453.

Improve output if no_lookup_host_duplicates test fails

If the test fails, output the offending addresses and a helpful error message.
Also slightly improve legibility of the preceding line that puts the addresses
into a HashMap.

Move std::os::raw::c_void into libcore and re-export in libstd

Implements the first part of [RFC 2521](https://github.com/rust-lang/rfcs/pull/2521).

cc #53856

resolve: Do not error on access to proc macros imported with `#[macro_use]`

This error is artificial, but previously, when `#[macro_use] extern crate x;` was stable, but non-derive proc macros were not, it worked like kind of a feature gate. Now both features are stable, so the error is no longer necessary.

This PR simplifies how `#[macro_use] extern crate x;` works - it takes all items from macro namespace of `x`'s root and puts them into macro prelude from which they all can now be accessed.

fix some uses of pointer intrinsics with invalid pointers

[Found by miri](https://github.com/solson/miri/pull/446):

* `Vec::into_iter` calls `ptr::read` (and the underlying `copy_nonoverlapping`) with an unaligned pointer to a ZST. [According to LLVM devs](https://bugs.llvm.org/show_bug.cgi?id=38583), this is UB because it contradicts the metadata we are attaching to that pointer.
* `HashMap` creation calls `ptr:.write_bytes` on a NULL pointer with a count of 0. This is likely not currently UB *currently*, but it violates the rules we are setting in https://github.com/rust-lang/rust/pull/53783, and we might want to exploit those rules later (e.g. with more `nonnull` attributes for LLVM).

    Probably what `HashMap` really should do is use `NonNull::dangling()` instead of 0 for the empty case, but that would require a more careful analysis of the code.

It seems like ideally, we should do a review of usage of such intrinsics all over libstd to ensure that they use valid pointers even when the size is 0. Is it worth opening an issue for that?

Rollup of 5 pull requests

Successful merges:

 - #53941 (rustdoc: Sort implementors)
 - #54181 (Suggest && and || instead of 'and' and 'or')
 - #54209 (Partially revert 674a5db1 "Fix undesirable fallout [from macro modularization]")
 - #54213 (De-overlap the lifetimes of `flow_inits` and `flow_{un,ever_}inits`.)
 - #54244 (Add a small search box to seach Rust's standary library)

Failed merges:

r? @ghost

Add a small search box to seach Rust's standary library

This change partially addresses #14572. No CSS doesn't look fancy
but at least it is functional.

De-overlap the lifetimes of `flow_inits` and `flow_{un,ever_}inits`.

This reduces `max-rss` for an `nll-check` build by 27% for `keccak`, and
by 8% for `inflate`.

r? @nikomatsakis

Partially revert 674a5db1 "Fix undesirable fallout [from macro modularization]"

Partially revert https://github.com/rust-lang/rust/commit/674a5db1a50e25dd60a8ee6669edee9a366c9fab

~~Closes~~ (see pnkfelix comments below) https://github.com/rust-lang/rust/issues/53675

Suggest && and || instead of 'and' and 'or'

Resolves #54109.

Note: competing pull reqeust: #54179

r? @csmoe

rustdoc: Sort implementors

Fixes #53812

use structured suggestion for "missing mut" label

Fixes #54133 for both NLL and non-NLL.

r? @estebank

I'm not super happy with the existing wording here, since it's now a suggestion. I wonder if the message would work better as something like "help: make binding mutable: `mut foo`"?

Also, are the `HELP` and `SUGGESTION` comments necessary?

stabilize slice_align_to

This is very hard to implement correctly, and leads to [serious bugs](https://github.com/llogiq/bytecount/pull/42) when done incorrectly. Moreover, this is needed to be able to run code that opportunistically exploits alignment on miri. So code using `align_to`/`align_to_mut` gets the benefit of a well-tested implementation *and* of being able to run in miri to test for (some kinds of) UB.

This PR also clarifies the guarantee wrt. the middle part being as long as possible.  Should the docs say under which circumstances the middle part could be shorter? Currently, that can only happen when running in miri.

rustc_resolve: allow only core, std, meta and --extern in Rust 2018 paths.

As per https://github.com/rust-lang/rust/issues/53166#issuecomment-419265401:
* Rust 2018 imports can no longer refer to crates not in "extern prelude"
  * `::foo` won't load a crate named `foo` unless `foo` is in the "extern prelude"
  * `extern crate foo;`, however, remains unchanged (can load arbitrary crates)
* `--extern crate_name` is added (note the lack of `=path`) as an unstable option
  * adds `crate_name` to the "extern prelude" (see above)
  * crate is searched in sysroot & library paths, just like `extern crate crate_name`.
  * `Cargo` support will be added later
* `core`, `std` and ~~`proc_macro`~~ `meta` are *always* available in the extern prelude
  * warning for interaction with `no_std` / `no_core` will be added later
  * **EDIT**: `proc_macro` was replaced by `meta`, see https://github.com/rust-lang/rust/issues/53166#issuecomment-421137230
    * note that there is no crate named `meta` being added, so `use meta::...;` will fail, we're only whitelisting it so we can start producing `uniform_paths` compatibility errors

Fixes #54006 (as the example now requires `--extern alloc`, which is unstable).
Fixes #54253 (hit during fixing RLS).

r? @petrochenkov cc @aturon @alexcrichton @Centril @joshtriplett

This reverts commit 9f53c87b, reversing
changes made to cba0fdf4.

If the test fails, output the offending addresses and a helpful error message.
Also slightly improve legibility of the preceding line that puts the addresses
into a HashMap.

Add option to run all tests

This adds the "--include-ignored" flag to libtest, which allows running ignored and unignored tests in one go.

Closes #50363

keep around some information for dead allocations so that we can use it to make sure a dangling ptr aligned and non-NULL

Add inspection and setter methods to proc_macro::Diagnostic.

A few useful methods for `proc_macro::Diagnostic`.

r? @alexcrichton

Update Clippy

Clippy one commit behind #54226. This should work

r? @Manishearth

Remove bitslice.rs

As the comment in `bitslice.rs` says:

> FIXME: merge with `bitvec`

This change partially addresses #14572. No CSS doesn't look fancy
but at least it is functional.

The way it defines implementations is unrealistic though.

A few cleanups for hir

- prefer `if let` to `match` when only 1 branch matters
- `chain` iterable items that are looped over in sequence
- `sort_by_key` instead of `sort_by` when possible
- change cloning `map`s to `cloned()`
- use `unwrap_or_else` and `ok` when applicable
- a few other minor readability improvements
- whitespace fixes