`sip::Hasher::short_write` is currently unused. It is called by
`sip::Hasher::write_{u8,usize}`, but those methods are also unused,
because `DefaultHasher`, `SipHasher` and `SipHasher13` don't implement
any of the `write_xyz` methods, so all their write operations end up
calling `sip::Hasher::write`.

(I confirmed this by inserting a `panic!` in `sip::Hasher::short_write`
and running the tests -- they all passed.)

The alternative would be to add all the missing `write_xyz` methods.
This does give some significant speed-ups, but it hurts compile times a
little in some cases. See rust-lang#69152 for details. This commit does the
conservative thing and doesn't change existing behaviour.

… style

For some reason the absolute paths were formatted differently on the
armhf-gnu target.

    thread '<unnamed>' panicked at 'assertion failed: `(left == right)`
      left: `"Backtrace [\n    { fn: \"__rust_maybe_catch_panic\" },\n    { fn: \"std::rt::lang_start_internal\", file: \"./rust/rt.rs\", line: 300 },\n    { fn: \"std::rt::lang_start\", file: \"./rust/rt.rs\", line: 400 },\n]"`,
     right: `"Backtrace [\n    { fn: \"__rust_maybe_catch_panic\" },\n    { fn: \"std::rt::lang_start_internal\", file: \"/rust/rt.rs\", line: 300 },\n    { fn: \"std::rt::lang_start\", file: \"/rust/rt.rs\", line: 400 },\n]"`', src/libstd/backtrace.rs:486:5

…d a long lost assertion

This reverts part of commit 9712fa4.

Co-Authored-By: Ralf Jung <[email protected]>

This commit fixes an issue where if `eprintln!` is used in a TLS
destructor it can accidentally cause the process to abort. TLS
destructors are executed after `main` returns on the main thread, and at
this point we've also deinitialized global `Lazy` values like those
which store the `Stderr` and `Stdout` internals. This means that despite
handling TLS not being accessible in `eprintln!`, we will fail due to
not being able to call `stderr()`. This means that we'll double-panic
quickly because panicking also attempt to write to stderr.

The fix here is to reimplement the global stderr handle to avoid the
need for destruction. This avoids the need for `Lazy` as well as the
hidden panic inside of the `stderr` function.

Overall this should improve the robustness of printing errors and/or
panics in weird situations, since the `stderr` accessor should be
infallible in more situations.

Backtrace Debug tweaks

- Change Debug representation of disabled and unsupported backtraces to use \<placeholder\> style, same as what we do for debug printing locked mutexes and mutably borrowed refcells;

    ```diff
    - Error { msg: "...", backtrace: disabled backtrace }
    + Error { msg: "...", backtrace: <disabled> }
    ```

- Remove quotes around unresolved symbol names;

    ```diff
    - Backtrace [{ fn: "<unknown>" }]
    + Backtrace [{ fn: <unknown> }]
    ```

- Add quotes around file paths;

    ```diff
    - Backtrace [{ fn: "krate::main", file: /path/to/main.rs, line: 10 }]
    + Backtrace [{ fn: "krate::main", file: "/path/to/main.rs", line: 10 }]
    ```

- Add test.

…te, r=dtolnay

Remove `sip::Hasher::short_write`.

`sip::Hasher::short_write` is currently unused. It is called by
`sip::Hasher::write_{u8,usize}`, but those methods are also unused,
because `DefaultHasher`, `SipHasher` and `SipHasher13` don't implement
any of the `write_xyz` methods, so all their write operations end up
calling `sip::Hasher::write`.

(I confirmed this by inserting a `panic!` in `sip::Hasher::short_write`
and running the tests -- they all passed.)

The alternative would be to add all the missing `write_xyz` methods.
This does give some significant speed-ups, but it hurts compile times a
little in some cases. See rust-lang#69152 for details. This commit does the
conservative thing and doesn't change existing behaviour.

r? @rust-lang/libs

…lfJung

Compute the correct layout for variants of uninhabited enums

r? @eddyb
cc @RalfJung

fixes rust-lang#69191
cc rust-lang#69763

…lacrum

Regenerate tables for Unicode 13.0.0

…hewjasper

Increase verbosity when suggesting subtle code changes

Do not suggest changes that are actually quite small inline, to minimize the likelihood of confusion.

Fix rust-lang#69243.

…fackler

Fix abort-on-eprintln during process shutdown

This commit fixes an issue where if `eprintln!` is used in a TLS
destructor it can accidentally cause the process to abort. TLS
destructors are executed after `main` returns on the main thread, and at
this point we've also deinitialized global `Lazy` values like those
which store the `Stderr` and `Stdout` internals. This means that despite
handling TLS not being accessible in `eprintln!`, we will fail due to
not being able to call `stderr()`. This means that we'll double-panic
quickly because panicking also attempt to write to stderr.

The fix here is to reimplement the global stderr handle to avoid the
need for destruction. This avoids the need for `Lazy` as well as the
hidden panic inside of the `stderr` function.

Overall this should improve the robustness of printing errors and/or
panics in weird situations, since the `stderr` accessor should be
infallible in more situations.

Add self to .mailmap

The variants are only used for [rust-lang/rust-clippy](https://github.com/rust-lang/rust-clippy), but it seems like <https://thanks.rust-lang.org/> only uses this `.mailmap`.