The existing code seems to assume that substitutions spans are disjoint,
which is not always the case.

In the example:

    pub trait AAAA {}
    pub trait B {}
    pub trait C {}
    pub type T<P: AAAA + B + C> = P;

, we get three substituions starting from ':' and ending respectively at
the end of each trait token.

With the former offset calculation, this would cause `underline_start` to
eventually become negative before being converted to `usize`...

The new version may report erroneous results for non perfectly overlapping
substitutions but I don't know if such examples exist. Alternatively, we
could detect these cases and trim out overlapping substitutions.

Consts now have a `fmt::Display` impl, so we can just use that to pretty-print.

We see multiple cases inside rustc and ecosystem code where ThreadId is
transmuted to u64, exploiting the underlying detail. This is suboptimal
(can break unexpectedly if we change things in std).

It is unlikely that ThreadId will ever need to be larger than u64 --
creating even 2^32 threads over the course of a program is quite hard,
2^64 is even harder. As such, we do not choose to return a larger sized
type (e.g. u128). If we choose to shrink ThreadId in the future, or
otherwise change its internals, it is likely that a mapping to u64 will
still be applicable (though may become more complex).

Also add unit tests

…excrichton

Add an unstable conversion from thread ID to u64

We see multiple cases inside rustc and ecosystem code where ThreadId is
transmuted to u64, exploiting the underlying detail. This is suboptimal
(can break unexpectedly if we change things in std).

It is unlikely that ThreadId will ever need to be larger than u64 --
creating even 2^32 threads over the course of a program is quite hard,
2^64 is even harder. As such, we do not choose to return a larger sized
type (e.g. u128). If we choose to shrink ThreadId in the future, or
otherwise change its internals, it is likely that a mapping to u64 will
still be applicable (though may become more complex).

I will file a tracking issue as soon as this is loosely approved.

Account for `type X = impl Trait;` in lifetime suggestion

Fix rust-lang#67619.

…alexcrichton

Stabilise vec::remove_item

Closes rust-lang#40062

r? @alexcrichton

Omit underscore constants from rustdoc

Underscore constants from rust-lang/rfcs#2526 / rust-lang#54912 do not correspond to a nameable item and so are never useful in documentation.
<br>

#### Before:

> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<img src="https://user-images.githubusercontent.com/1940490/71771409-0427cc80-2eef-11ea-8b7d-d9c74a873e7e.png" width="60%">

#### After:

> Not that.

Handle multiple error fix suggestions carefuly

The existing code seems to assume that substitutions spans are disjoint,
which is not always the case.

In the example:

    pub trait AAAA {}
    pub trait B {}
    pub trait C {}
    pub type T<P: AAAA + B + C> = P;

, we get three substituions starting from ':' and ending respectively at
the end of each trait token.

With the former offset calculation, this would cause `underline_start` to
eventually become negative before being converted to `usize`...

The new version may report erroneous results for non perfectly overlapping
substitutions but I don't know if such examples exist. Alternatively, we
could detect these cases and trim out overlapping substitutions.

Fixes rust-lang#67690

…, r=Centril

Improve hygiene of `newtype_index`

`newtype_index` no longer needs `rustc_index::vec::Idx` to be in scope.

r? @Centril

…r=GuillaumeGomez

rustdoc: HTML escape const values

r? @GuillaumeGomez

…dtwco

Fix ICE in const pretty printing and resolve FIXME

Consts now have a `fmt::Display` impl, so we can just use that to pretty-print.

This resolves an ICE in rust-lang#61936, though it hits more ICEs afterwards. I couldn't find a test case that was resolved by this that didn't hit errors later on.

Formatting an example for method Vec.retain

…lan-DPC

Clean up E0178 explanation

r? @Dylan-DPC

fire "non_camel_case_types" for associated types

Fixes rust-lang#67920.

Missing module std in example.

Update books

## nomicon

1 commits in 8be35b201f9cf0a4c3fcc96c83ac21671dcf3112..3e6e1001dc6e095dbd5c88005e80969f60e384e1
2019-12-01 13:02:12 -0500 to 2019-12-14 22:08:52 +0000
- Remove mention of contravariance possibly getting scrapped (rust-lang/nomicon#177)

## reference

4 commits in d8dfe1b..e115753
2019-12-14 21:04:58 +0100 to 2019-12-22 13:13:14 +0100
- Fix typo in macros-by-example.md (rust-lang/reference#733)
- Remove `extern` from exception list (rust-lang/reference#732)
- Added clearification that closures are refered to lambdas (rust-lang/reference#731)
- abi.md: clarify #[used] and linking (rust-lang/reference#712)

## book

2 commits in ef8bb568035ded8ddfa30a9309026638cc3c8136..5c5cfd2e94cd42632798d9bd3d1116133e128ac9
2019-11-28 11:00:04 -0600 to 2019-12-16 09:27:21 -0600
- document new --show-output option in ch 11-2 (Rust >= 1.39) (rust-lang/book#2065)
- Fix sentence in ch07 (rust-lang/book#2183)

## rust-by-example

3 commits in b7ac1bc76b7d02a43c83b3a931d226f708aa1ff4..1d59403cb5269c190cc52a95584ecc280345495a
2019-12-02 11:38:43 -0300 to 2019-12-27 08:27:05 -0300
- Enable section-folding of table of content (rust-lang/rust-by-example#1290)
- Remove unnecessary lifetime annotation (rust-lang/rust-by-example#1300)
- eliminate the warnings (rust-lang/rust-by-example#1301)

## edition-guide

1 commits in 6601cab4666596494a569f94aa63b7b3230e9769..1a2390247ad6d08160e0dd74f40a01a9578659c2
2019-11-22 12:08:58 -0500 to 2019-12-29 10:40:55 -0800
- Updated install and uninstall instructions (rust-lang/edition-guide#194)

## embedded-book

1 commits in c26234930282210849256e4ecab925f0f2daf3be..9493b7d4dc97eda439bd8780f05ad7b234cd1cd7
2019-12-07 17:25:11 +0000 to 2019-12-27 20:05:00 +0000
- fixed typo in Interrupts.md  (rust-embedded/book#218)