In the old setup, if the dereffed-to item has multiple impl blocks,
each one gets its own `div.impl-items` in the section, but there
are no headers separating them. Since the last method in a
`div.impl-items` has no bottom margin, and there are no margins
between these divs, there is no margin between the last method
of one impl and the first method of the following impl.

This patch fixes it by simplifying the HTML. Each Deref block gets
exactly one `div.impl-items`, no matter how many impl blocks it
actually has.

`rustc_arena`.

…ectory

This fixes the following recurring error on windows:
```
Traceback (most recent call last):
  File "C:\Users\jyn\src\rust\x.py", line 29, in <module>
    bootstrap.main()
  File "C:\Users\jyn\src\rust\src\bootstrap\bootstrap.py", line 963, in main
    bootstrap(args)
  File "C:\Users\jyn\src\rust\src\bootstrap\bootstrap.py", line 927, in bootstrap
    build.download_toolchain()
  File "C:\Users\jyn\src\rust\src\bootstrap\bootstrap.py", line 437, in download_toolchain
    shutil.rmtree(bin_root)
  File "C:\Users\jyn\AppData\Local\Programs\Python\Python311\Lib\shutil.py", line 759, in rmtree
    return _rmtree_unsafe(path, onerror)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\jyn\AppData\Local\Programs\Python\Python311\Lib\shutil.py", line 617, in _rmtree_unsafe
    _rmtree_unsafe(fullname, onerror)
  File "C:\Users\jyn\AppData\Local\Programs\Python\Python311\Lib\shutil.py", line 622, in _rmtree_unsafe
    onerror(os.unlink, fullname, sys.exc_info())
  File "C:\Users\jyn\AppData\Local\Programs\Python\Python311\Lib\shutil.py", line 620, in _rmtree_unsafe
    os.unlink(fullname)
PermissionError: [WinError 5] Access is denied: 'C:\\Users\\jyn\\src\\rust\\build\\x86_64-pc-windows-msvc\\stage0\\bin\\rust-analyzer-proc-macro-srv.exe'
```

…omez,jyn514,notriddle

rustdoc: Add a new lint for broken inline code

This patch adds `rustdoc::unescaped_backticks`, a new rustdoc lint that will detect broken inline code nodes.

The lint woks by finding stray backticks and with some heuristics tries to guess where the second backtick might be missing.

Here is how it looks:
```rust
#![warn(rustdoc::unescaped_backticks)]

/// `add(a, b) is the same as `add(b, a)`.
pub fn add(a: i32, b: i32) -> i32 { a + b }
```
```text
warning: unescaped backtick
 --> src/lib.rs:3:41
  |
3 | /// `add(a, b) is the same as `add(b, a)`.
  |                                         ^
  |
help: a previous inline code might be longer than expected
  |
3 | /// `add(a, b)` is the same as `add(b, a)`.
  |               +
help: if you meant to use a literal backtick, escape it
  |
3 | /// `add(a, b) is the same as `add(b, a)\`.
  |                                         +
```

If we can't get proper spans, for example if the doc comment comes from a macro expansion, we print the suggestion in help messages instead. Here's a [real-world example](https://docs.rs/tracing-subscriber/0.3.17/tracing_subscriber/layer/trait.Filter.html#method.max_level_hint):

```text
warning: unescaped backtick
    --> /tracing-subscriber-0.3.17/src/layer/mod.rs:1400:9
     |
1400 | /         /// Returns an optional hint of the highest [verbosity level][level] that
1401 | |         /// this `Filter` will enable.
1402 | |         ///
1403 | |         /// If this method returns a [`LevelFilter`], it will be used as a hint to
...    |
1427 | |         /// [`Interest`]: tracing_core::subscriber::Interest
1428 | |         /// [rebuild]: tracing_core::callsite::rebuild_interest_cache
     | |_____________________________________________________________________^
     |
     = help: a previous inline code might be longer than expected
              change: Therefore, if the `Filter will change the value returned by this
             to this: Therefore, if the `Filter` will change the value returned by this
     = help: if you meant to use a literal backtick, escape it
              change: [`rebuild_interest_cache`][rebuild] is called after the value of the max
             to this: [`rebuild_interest_cache\`][rebuild] is called after the value of the max
```

You can find more examples [here](https://gist.github.com/lukas-code/7678ddf5c608aee97b3a669de80d3465).

A limitation of the current implementation is, that it cannot suggest removing misplaced backticks, for example [here](https://docs.rs/tikv-jemalloc-sys/0.5.3+5.3.0-patched/tikv_jemalloc_sys/fn.mallctl.html).

The lint is allowed by default ~~and nightly-only~~ for now, ~~but without a feature gate. This is similar to how `rustdoc::invalid_html_tags` and `rustdoc::bare_urls` were handled.~~

…etrochenkov

Add `force` option for `--extern` flag

When `--extern force:foo=libfoo.so` is passed to `rustc` and `foo` is not actually used in the crate, ~inject an `extern crate foo;` statement into the AST~ force it to be resolved anyway in `CrateLoader::postprocess()`. This allows you to, for instance, inject a `#[panic_handler]` implementation into a `#![no_std]` crate without modifying its source so that it can be built as a `dylib`. It may also be useful for `#![panic_runtime]` or `#[global_allocator]`/`#![default_lib_allocator]` implementations.

My work previously involved integrating Rust into an existing C/C++ codebase which was built with Buck and shipped on, among other platforms, Android. When targeting Android, Buck builds all "native" code with shared linkage* so it can be loaded from Java/Kotlin. My project was not itself `#![no_std]`, but many of our dependencies were, and they would fail to build with shared linkage due to a lack of a panic handler. With this change, that project can add the new `force` option to the `std` dependency it already explicitly provides to every crate to solve this problem.

*This is an oversimplification - Buck has a couple features for aggregating dependencies into larger shared libraries, but none that I think sustainably solve this problem.

~The AST injection happens after macro expansion around where we similarly inject a test harness and proc-macro harness. The resolver's list of actually-used extern flags is populated during macro expansion, and if any of our `--extern` arguments have the `force` option and weren't already used, we inject an `extern crate` statement for them. The injection logic was added in `rustc_builtin_macros` as that's where similar injections for tests, proc-macros, and std/core already live.~

(New contributor - grateful for feedback and guidance!)

…sts, r=Mark-Simulacrum

Update tests for libtest `--format json`

This PR makes the test work on beta and stable, and adds a test ensuring the option is not available on beta and stable. Backported these commits from rust-lang#110414.

… r=Nilstrieb

Deny the `unsafe_op_in_unsafe_fn` lint in `rustc_arena`.

r? `@Nilstrieb`

…GuillaumeGomez

rustdoc: fix weird margins between Deref impl items

## Before

![image](https://user-images.githubusercontent.com/1593513/235245977-90770591-22c1-4a27-9464-248a3729a2b7.png)

## After

![image](https://user-images.githubusercontent.com/1593513/235246009-0e83113e-42b7-4e29-981d-969f9d20af01.png)

## Description

In the old setup, if the dereffed-to item has multiple impl blocks, each one gets its own `div.impl-items` in the section, but there are no headers separating them. Since the last method in a `div.impl-items` has no bottom margin, and there are no margins between these divs, there is no margin between the last method of one impl and the first method of the following impl.

This patch fixes it by simplifying the HTML. Each Deref block gets exactly one `div.impl-items`, no matter how many impl blocks it actually has.

windows: kill rust-analyzer-proc-macro-srv before deleting stage0 directory

This fixes the following recurring error on windows:
```
Traceback (most recent call last):
  File "C:\Users\jyn\src\rust\x.py", line 29, in <module>
    bootstrap.main()
  File "C:\Users\jyn\src\rust\src\bootstrap\bootstrap.py", line 963, in main
    bootstrap(args)
  File "C:\Users\jyn\src\rust\src\bootstrap\bootstrap.py", line 927, in bootstrap
    build.download_toolchain()
  File "C:\Users\jyn\src\rust\src\bootstrap\bootstrap.py", line 437, in download_toolchain
    shutil.rmtree(bin_root)
  File "C:\Users\jyn\AppData\Local\Programs\Python\Python311\Lib\shutil.py", line 759, in rmtree
    return _rmtree_unsafe(path, onerror)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\jyn\AppData\Local\Programs\Python\Python311\Lib\shutil.py", line 617, in _rmtree_unsafe
    _rmtree_unsafe(fullname, onerror)
  File "C:\Users\jyn\AppData\Local\Programs\Python\Python311\Lib\shutil.py", line 622, in _rmtree_unsafe
    onerror(os.unlink, fullname, sys.exc_info())
  File "C:\Users\jyn\AppData\Local\Programs\Python\Python311\Lib\shutil.py", line 620, in _rmtree_unsafe
    os.unlink(fullname)
PermissionError: [WinError 5] Access is denied: 'C:\\Users\\jyn\\src\\rust\\build\\x86_64-pc-windows-msvc\\stage0\\bin\\rust-analyzer-proc-macro-srv.exe'
```

Fixes rust-lang#107018.

r? `@ChrisDenton`