support revealing uses of opaques

[lcnr]

the following now works, needs a bit of cleanup to actually land :3

fn foo(x: &u32) -> impl Sized + '_ {
    let _ = || {
        let temp = 1;
        // normalization of the return type results
        // in `opaque<'local1> = &'local2 u32`.
        foo(&temp);
    };
    x
}

final breakage?

fn proj<F: FnOnce() -> P, P: Iterator<Item = Q>, Q>(_: F) {}
struct Lts<'a, 'b>(&'a (), &'b ());
fn expectations<'a>() -> impl Iterator<Item = Lts<'a, 'static>> + use<'a> {
    // opaque<'a> = Map<std::iter::Empty<Lts<'0, '1>>, {closure@src/main.rs:5:28: 5:31}>``
    proj::<_, _, Lts<'a, 'static>>(|| expectations());
    std::iter::empty().map(|x| x)
}

struct Foo<F, T>(T, F);
trait Trait {
    type Assoc;
}
impl<F: FnOnce(T) -> R, T, R> Trait for Foo<F, T> {
    type Assoc = R;
}

fn new_defining_use<F: FnOnce() -> R, R>(f: F) {}
fn rpit<'a>() -> impl Trait<Assoc = &'static ()> + use<'a> {
    new_defining_use(rpit::<'a>);
    Foo(&(), |x: &'static ()| x)
}

use std::convert::identity;
struct Foo<F, T>(T, F);
trait Trait {
    type Assoc;
}
impl<F: FnOnce(T) -> R, T, R> Trait for Foo<F, T> {
    type Assoc = R;
}

fn new_defining_use<F: FnOnce() -> R, R>(_: F) {}
fn rpit<'a>() -> impl Trait<Assoc = &'static ()> + use<'a> {
    new_defining_use(rpit::<'a>);
    Foo(&(), identity as fn(_) -> _)
}

struct Inv<'a, 'b>(*mut (&'a (), &'b ()));
fn new_defining_use<F: FnOnce() -> R, R>(_: F) {}
fn rpit<'a>() -> impl Sized + use<'a> {
    new_defining_use(rpit::<'a>);
    Inv::<'a, 'static>(std::ptr::null_mut())
}

fn new_defining_use<F: FnOnce(T) -> R, T, R>(_: F) {}
fn rpit<'a,  'b: 'b>(x: &'b ()) -> impl Sized + use<'a, 'b> {
    new_defining_use(rpit::<'a, 'b>);
    x
}

r? @compiler-errors

[lcnr]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 22d34c4 with merge 14ea441...

[bors]

☀️ Try build successful - checks-actions
Build commit: 14ea441 (14ea4416942169f85851de68119f43a59ef8801f)

[rust-timer]

Finished benchmarking commit (14ea441): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

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)	0.6%	[0.2%, 1.1%]	62
Regressions ❌ (secondary)	0.5%	[0.3%, 0.8%]	16
Improvements ✅ (primary)	-0.3%	[-0.3%, -0.2%]	2
Improvements ✅ (secondary)	-0.5%	[-1.1%, -0.2%]	27
All ❌✅ (primary)	0.5%	[-0.3%, 1.1%]	64

Max RSS (memory usage)

Results (primary 2.0%, secondary -1.3%)

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)	2.0%	[1.2%, 2.8%]	5
Regressions ❌ (secondary)	3.1%	[2.5%, 3.6%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.0%	[-7.2%, -1.2%]	5
All ❌✅ (primary)	2.0%	[1.2%, 2.8%]	5

Cycles

Results (primary 1.1%, secondary 1.5%)

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)	1.1%	[0.8%, 1.3%]	12
Regressions ❌ (secondary)	1.5%	[1.2%, 1.9%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.1%	[0.8%, 1.3%]	12

Binary size

Results (secondary -0.1%)

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	6
All ❌✅ (primary)	-	-	0

Bootstrap: 780.245s -> 782.612s (0.30%)
Artifact size: 366.19 MiB -> 366.30 MiB (0.03%)

[craterbot]

🚧 Experiment pr-139587-1 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[craterbot]

🎉 Experiment pr-139587-1 is completed!
📊 1134 regressed and 7 fixed (626689 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[lcnr]

@bors try

[bors]

⌛ Trying commit 4028ea1 with merge 6cbf54b...

[bors]

☀️ Try build successful - checks-actions
Build commit: 6cbf54b (6cbf54b1453b438241487f195740266bb9d8c8ba)

[lcnr]

@craterbot check crates=https://crater-reports.s3.amazonaws.com/pr-139587-1/retry-regressed-list.txt p=1

[craterbot]

🚨 Error: database is locked

🆘 If you have any trouble with Crater please ping @rust-lang/infra!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[lcnr]

@craterbot check crates=https://crater-reports.s3.amazonaws.com/pr-139587-1/retry-regressed-list.txt p=1

[craterbot]

👌 Experiment pr-139587-2 created and queued.
🤖 Automatically detected try build 6cbf54b
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[rust-log-analyzer]

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

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

info: removing rustup binaries
info: rustup is uninstalled
##[group]Image checksum input
mingw-check-tidy
# We use the ghcr base image because ghcr doesn't have a rate limit
# and the mingw-check-tidy job doesn't cache docker images in CI.
FROM ghcr.io/rust-lang/ubuntu:22.04

ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update && apt-get install -y --no-install-recommends \
  g++ \
---

COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
COPY host-x86_64/mingw-check/validate-error-codes.sh /scripts/

# NOTE: intentionally uses python2 for x.py so we can test it still works.
# validate-toolstate only runs in our CI, so it's ok for it to only support python3.
ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test \
           --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
#
# This file is autogenerated by pip-compile with Python 3.10
# by the following command:
#
#    pip-compile --allow-unsafe --generate-hashes reuse-requirements.in
---
#12 2.957 Building wheels for collected packages: reuse
#12 2.958   Building wheel for reuse (pyproject.toml): started
#12 3.175   Building wheel for reuse (pyproject.toml): finished with status 'done'
#12 3.176   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132719 sha256=d2a2565e7037ad3883fb9337653f2e25bbb588534fbef3697286cbc26d1bf634
#12 3.176   Stored in directory: /tmp/pip-ephem-wheel-cache-1jmvwu47/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#12 3.178 Successfully built reuse
#12 3.179 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#12 3.585 Successfully installed attrs-23.2.0 binaryornot-0.4.4 boolean-py-4.0 chardet-5.2.0 jinja2-3.1.4 license-expression-30.3.0 markupsafe-2.1.5 python-debian-0.1.49 reuse-4.0.3 tomlkit-0.13.0
#12 3.586 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#12 4.136 Collecting virtualenv
#12 4.198   Downloading virtualenv-20.31.2-py3-none-any.whl (6.1 MB)
#12 4.434      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 6.1/6.1 MB 26.1 MB/s eta 0:00:00
#12 4.496 Collecting platformdirs<5,>=3.9.1
#12 4.504   Downloading platformdirs-4.3.8-py3-none-any.whl (18 kB)
#12 4.546 Collecting filelock<4,>=3.12.2
#12 4.554   Downloading filelock-3.18.0-py3-none-any.whl (16 kB)
#12 4.576 Collecting distlib<1,>=0.3.7
#12 4.585   Downloading distlib-0.3.9-py2.py3-none-any.whl (468 kB)
#12 4.595      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 469.0/469.0 KB 54.2 MB/s eta 0:00:00
#12 4.677 Installing collected packages: distlib, platformdirs, filelock, virtualenv
#12 4.871 Successfully installed distlib-0.3.9 filelock-3.18.0 platformdirs-4.3.8 virtualenv-20.31.2
#12 4.871 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#12 DONE 5.0s

#13 [7/8] COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
#13 DONE 0.0s
---
DirectMap4k:      139200 kB
DirectMap2M:    10346496 kB
DirectMap1G:     8388608 kB
##[endgroup]
Executing TIDY_PRINT_DIFF=1 python2.7 ../x.py test            --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
+ TIDY_PRINT_DIFF=1 python2.7 ../x.py test --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
##[group]Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.05s
##[endgroup]
WARN: currently no CI rustc builds have rustc debug assertions enabled. Please either set `rust.debug-assertions` to `false` if you want to use download CI rustc or set `rust.download-rustc` to `false`.
[TIMING] core::build_steps::tool::LibcxxVersionTool { target: x86_64-unknown-linux-gnu } -- 0.216
---
fmt check
fmt: checked 6008 files
tidy check
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/compiler/rustc_borrowck/src/region_infer/opaque_types.rs:420: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
##[error]tidy error: /checkout/compiler/rustc_borrowck/src/region_infer/opaque_types.rs:477: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
tidy error: /checkout/tests/ui/nll/member-constraints/non-root-universe-existential-1.rs: too many trailing newlines (3)
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'venv'
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'virtualenv'
Requirement already satisfied: pip in ./build/venv/lib/python3.10/site-packages (25.1.1)
linting python files
All checks passed!
checking python file formatting
26 files already formatted
checking C++ file formatting
some tidy checks failed
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:01:58
  local time: Fri May  9 02:54:15 UTC 2025
  network time: Fri, 09 May 2025 02:54:15 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[craterbot]

🚧 Experiment pr-139587-2 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[craterbot]

🎉 Experiment pr-139587-2 is completed!
📊 3 regressed and 0 fixed (4264 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[rustbot]

Requested reviewer is already assigned to this pull request.

Please choose another assignee.

[bors]

☔ The latest upstream changes (presumably #141066) made this pull request unmergeable. Please resolve the merge conflicts.

[lcnr]

closing in favor of #145925