Implement a lint for implicit autoref of raw pointer dereference - take 2

[Urgau]

t-lang nomination comment

This PR aims at implementing a lint for implicit autoref of raw pointer dereference, it is based on #103735 with suggestion and improvements from #103735 (comment).

The goal is to catch cases like this, where the user probably doesn't realise it just created a reference.

pub struct Test {
    data: [u8],
}

pub fn test_len(t: *const Test) -> usize {
    unsafe { (*t).data.len() }  // this calls <[T]>::len(&self)
}

Since #103735 already went 2 times through T-lang, where they T-lang ended-up asking for a more restricted version (which is what this PR does), I would prefer this PR to be reviewed first before re-nominating it for T-lang.

---

Compared to the PR it is as based on, this PR adds 3 restrictions on the outer most expression, which must either be:

1. A deref followed by any non-deref place projection (that intermediate deref will typically be auto-inserted)
2. A method call annotated with #[rustc_no_implicit_refs].
3. A deref followed by a addr_of! or addr_of_mut!. See bottom of post for details.

There are several points that are not 100% clear to me when implementing the modifications:

• "4. Any number of automatically inserted deref/derefmut calls." I as never able to trigger this. Am I missing something? Fixed
• Are "index" and "field" enough?

---

cc @JakobDegen @WaffleLapkin
r? @RalfJung

try-job: dist-various-1
try-job: dist-various-2

[rustbot]

The Miri subtree was changed

cc @rust-lang/miri

[RalfJung]

Sorry, I can't take on more reviews currently.
r? compiler
(or feel free to pick someone specific who's suited)

[Dylan-DPC]

@Urgau if you can rebase the latest conflicts we can push this forward and maybe get it reviewed by another reviewer

[Urgau]

@Dylan-DPC rebased.

@rustbot review

[rust-timer]

Finished benchmarking commit (a932eb3): comparison URL.

Overall result: ❌ regressions - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

• If the regression was expected or you think it can be justified,
  please write a comment with sufficient written justification, and add
  @rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
• If you think that you know of a way to resolve the regression, try to create
  a new PR with a fix for the regression.
• If you do not understand the regression or you think that it is just noise,
  you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
  were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	1.8%	[0.3%, 3.6%]	6
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.8%	[0.3%, 3.6%]	6

Max RSS (memory usage)

Results (primary 0.4%, secondary -0.5%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.2%	[0.5%, 2.3%]	4
Regressions ❌ (secondary)	2.8%	[2.8%, 2.8%]	1
Improvements ✅ (primary)	-0.6%	[-0.7%, -0.5%]	3
Improvements ✅ (secondary)	-2.2%	[-3.2%, -1.2%]	2
All ❌✅ (primary)	0.4%	[-0.7%, 2.3%]	7

Cycles

Results (primary 1.0%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.1%	[0.5%, 2.7%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-0.6%, -0.5%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.0%	[-0.6%, 2.7%]	7

Binary size

Results (primary 0.0%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	1

Bootstrap: 761.588s -> 761.378s (-0.03%)
Artifact size: 365.21 MiB -> 365.18 MiB (-0.01%)

[rylev]

The perf regression is reversed in #140406

@rustbot label: +perf-regression-triaged