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

[Urgau]

@bors try

[bors]

⌛ Trying commit 05f2b22 with merge 40da18f879506d0cf9879a1d61f68a52ba2c658f...

[bors]

☀️ Try build successful - checks-actions
Build commit: 40da18f (40da18f879506d0cf9879a1d61f68a52ba2c658f)

[Urgau]

@bors r=jdonszelmann,traviscross

[bors]

📌 Commit 05f2b22 has been approved by jdonszelmann,traviscross

It is now in the queue for this repository.

[bors]

⌛ Testing commit 05f2b22 with merge 5311e65...

[rust-log-analyzer]

The job x86_64-mingw-1 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

---- [run-make] tests\run-make\amdgpu-kd stdout ----

error: rmake recipe failed to complete
status: exit code: 1
command: "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\test\\run-make\\amdgpu-kd\\rmake.exe"
stdout: none
--- stderr -------------------------------
command failed at line 18
Command { cmd: "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\stage2\\bin\\rustc.exe" "-L" "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\test\\run-make\\amdgpu-kd\\rmake_out" "--crate-name" "foo" "--target=amdgcn-amd-amdhsa" "-Ctarget-cpu=gfx900" "--crate-type" "cdylib" "foo.rs", stdin_buf: None, stdin: None, stdout: None, stderr: None, drop_bomb: DropBomb { command: "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\stage2\\bin\\rustc.exe", defused: true, armed_location: Location { file: "D:\\a\\rust\\rust\\tests\\run-make\\amdgpu-kd\\rmake.rs", line: 12, col: 5 } }, already_executed: true }
output status: `exit code: 1`
=== STDOUT ===



=== STDERR ===
error: linking with `rust-lld` failed: exit code: 0xc0000374
  |
  = note: "rust-lld" "-flavor" "gnu" "--version-script=C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\rustcDK81Hk\\list" "--no-undefined-version" "<1 object files omitted>" "--as-needed" "-L" "C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\rustcDK81Hk\\raw-dylibs" "-Bdynamic" "--eh-frame-hdr" "-z" "noexecstack" "-L" "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\test\\run-make\\amdgpu-kd\\rmake_out" "-o" "foo.elf" "--gc-sections" "-shared"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: 

error: aborting due to 1 previous error
------------------------------------------
---
test result: FAILED. 279 passed; 1 failed; 110 ignored; 0 measured; 6 filtered out; finished in 199.20s

Some tests failed in compiletest suite=run-make mode=run-make host=x86_64-pc-windows-gnu target=x86_64-pc-windows-gnu
Build completed unsuccessfully in 2:25:17
make: *** [Makefile:124: ci-mingw-x] Error 1
  local time: Sun Apr 27 16:37:09 CUT 2025
  network time: Sun, 27 Apr 2025 16:37:09 GMT
##[error]Process completed with exit code 2.
Post job cleanup.
[command]"C:\Program Files\Git\bin\git.exe" version

[bors]

💔 Test failed - checks-actions

[Urgau]

CI error is unrelated to this PR. Seems spurious.

@bors retry

[bors]

⌛ Testing commit 05f2b22 with merge af9aa86f909dbc0990a114148a12f36a9ff4828f...

[Urgau]

@bors retry