Update Clippy

Biweekly Clippy Sync

r? @Manishearth

Fix FP `useless_conversion`

Fix #5833.

changelog: none

Add some regression tests

cc #56445
Fixes #72911

Miri rename undef uninit

Renamed parts of code within the `librustc_middle/mir/interpret/` directory.

Related issue [#71193](https://github.com/rust-lang/rust/issues/71193)

Remove trait LengthAtMost32

This is a continuation of https://github.com/rust-lang/rust/pull/74026 preserving the original burrbull's commit.

I talked to @burrbull, he suggested me to finish his PR.

Use the proper span when WF-checking an impl self type

Fix rustc docs typo.

Normalize bounds fully when checking defaulted types

When checking that the default type for `<T as X>::Y` is valid in this example:

```
trait X { type Y: PartialEq<<Self as X>::Y> }
impl X for T { default type Y = S; }
```

We will have to prove the bound `S: PartialEq<<T as X>::Y>`. In this case
we want `<T as X>::Y` to normalize to `S`. This is valid because we are
checking the default value specifically here. Add `<T as X>::Y = S` to the
ParamEnv for normalization _of the bound we are checking_ only.

Fixes #73818.

---

I noticed that adding this to the env for bounds checking didn't break any tests. Not sure if this is because we can't rely on it to prove anything, or because of missing test coverage.

r? @matthewjasper, @nikomatsakis

Update rustfmt and rls

Closes #74080, #74081.

rls changes:
- deps: update racer and cargo

rustfmt changes:
- preparation for potential rustfmt 1.4.19 (#4283)
- chore: backport 8157a3f0afe978d3e953420577f8344db7e905bf
- deps: bump rustc-ap to v669
- deps: bump rustc-ap-* to v668
- deps: bump rustc-ap* to v666
- Use correct span for match arms with the leading pipe and attributes (#3975)

Changes:
- preparation for potential rustfmt 1.4.19 (#4283)
- chore: backport 8157a3f0afe978d3e953420577f8344db7e905bf
- deps: bump rustc-ap to v669
- deps: bump rustc-ap-* to v668
- deps: bump rustc-ap* to v666
- Use correct span for match arms with the leading pipe and attributes (#3975)

Changes:
- deps: update racer and cargo

Clean up E0719 explanation

r? @Dylan-DPC

Detect turbofish missing surrounding angle brackets

Fix #74065.

renamed Allocation::check_defined_and_ptr to Allocation::check_init_and_ptr

renamed Allocation::check_defined_and_ptr to Allocation::check_init_and_ptr

in src/librustc_middle/mir/interpret/allocation.rs

renamed Allocation::is_defined and Allocation::check_defined, fixed documentation

renamed Allocation::is_defined and Allocation::check_defined to is_init and check_init respectively.

Fixed documentation so it correctly refers to "initialization" instead of "defined"-ness

renamed Allocation::mark_definedness

renamed Allocation::mark_definedness to Allocation::mark_init

Renamed new_state parameter in Allocation::mark_init

Renamed new_state to is_init, as the latter is more descriptive.

renamed functions in AllocationDefinedness

renamed AllocationDefinedness::all_bytes_undef and AllocationDefinedness::mark_compressed_undef_range to no_bytes_init and mark_compressed_init_range respectively.

renamed AllocationDefinedness to InitMaskCompressed

renamed Immediate::to_scalar_or_undef

renamed to to_scalar_or_uninit

fixed comment references to "undef"

Changed comments referring to "undef" and "definedness" to "initialization" and "initialization state" in src/librustc_mir/interpret/memory.rs and src/librustc_middle/mir/interpret/allocation.rs

changed references to "undef" in comments and a variable

Changed some comments referring to "undef" to use "uninitialized" instead. Also changed a variable from "undef_end" to "uninit_end".
All changes were made within src/librustc_middle/mir/interpret/allocation.rs.

Changed more comments referring to undef

Changed comments to use "uninitialized" instead of "undef" in src/librustc_middle/mir/interpret/allocation.rs.

Fix panic message when `RangeFrom` index is out of bounds

Before, the `Range` method was called with `end = slice.len()`. Unfortunately, because `Range::index` first checks the order of the indices (start has to be smaller than end), an out of bounds index leads to `core::slice::slice_index_order_fail` being called. This prints the message 'slice index starts at 27 but ends at 10', which is worse than 'index 27 out of range for slice of length 10'. This is not only useful to normal users reading panic messages, but also for people inspecting assembly and being confused by `slice_index_order_fail` calls.

You can see the produced assembly [here](https://rust.godbolt.org/z/GzMGWf) and try on Playground [here](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=aada5996b2f3848075a6d02cf4055743). (By the way. this is only about which panic function is called; I'm pretty sure it does not improve anything about performance).

Fix #5833.

re-add Layout::for_value_raw

Tracking issue: #69835

This was accidentally removed in #70362 56cbf2f2.
Originally added in #69079.

Improve documentation of `String::from_raw_parts`

Improve the documentation for Vec::drain

Fixes #73844.

@rusbot modify labels: A-collections, C-enhancement, T-doc, T-libs

Document the where keyword

Partial fix of #34601 (and last PR for it ).

This documents the `where` keyword.

@rustbot modify labels: T-doc,C-enhancement

Document the ref keyword

Partial fix for #34601.

This documents the `ref` keyword with two examples, one failing to compile because the `ref` keyword is missing, and the same example fixed with the keyword inserted in the correct place.

It also explains (very *very* rapidly) the differences between `&` and `ref`.

I put a link to the best place I could find in the Reference but there may be something better that I didn't find.

 Miri: use extern fn to expose interpreter operations to program; fix leak checker on Windows

This PR realizes an idea that @oli-obk has been suggesting for a while: to use Miri-specific `extern` functions to provide some extra capabilities to the program. Initially, we have two of these methods, which libstd itself needs:
* `miri_start_panic`, which replaces the intrinsic of the same name (mostly for consistency, to avoid having multiple mechanisms for Miri-specific functionality).
* `miri_static_root`, which adds an allocation to a list of static "roots" that Miri considers as not having leaked (including all memory reachable through them). This is needed for https://github.com/rust-lang/miri/issues/1302.

We use `extern` functions instead of intrinsics for this so that user code can more easily call these Miri hoolks -- e.g. `miri_static_root` should be useful for https://github.com/rust-lang/miri/issues/1318.

The Miri side of this is at https://github.com/rust-lang/miri/pull/1485.

r? @oli-obk

add `visit_operand` to const prop

r? @oli-obk

Rollup of 8 pull requests

Successful merges:

 - #72954 (revise RwLock for HermitCore)
 - #74367 (Rearrange the pipeline of `pow` to gain efficiency)
 - #74491 (Optimize away BitAnd and BitOr when possible)
 - #74639 (Downgrade glibc to 2.11.1 for ppc, ppc64 and s390x)
 - #74661 (Refactor `region_name`: add `RegionNameHighlight`)
 - #74692 (delay_span_bug instead of silent ignore)
 - #74698 (fixed error reporting for mismatched traits)
 - #74715 (Add a system for creating diffs across multiple mir optimizations.)

Failed merges:

r? @ghost