fix fn/const items implied bounds and wf check #104098

aliemjay · 2022-11-07T10:47:07Z

These are two distinct changes (edit: actually three, see below):

Wf-check all fn item args. This is a soundness fix.
Fixes function type params are not checked for well-formedness #104005
Use implied bounds from impl header in borrowck of associated functions/consts. This strictly accepts more code and helps to mitigate the impact of other breaking changes.
Fixes implied bounds from impl header are not used in associated functions/consts #98852
Fixes Generic param requires bounds on call to function that is already required for calls to the caller #102611

The first is a breaking change and will likely have a big impact without the the second one. See the first commit for how it breaks libstd.

Landing the second one without the first will allow more incorrect code to pass. For example an exploit of #104005 would be as simple as:

use core::fmt::Display;

trait ExtendLt<Witness> {
    fn extend(self) -> Box<dyn Display>;
}

impl<T: Display> ExtendLt<&'static T> for T {
    fn extend(self) -> Box<dyn Display> {
        Box::new(self)
    }
}

fn main() {
    let val = (&String::new()).extend();
    println!("{val}");
}

The third change is to to check WF of user type annotations before normalizing them (fixes #104764, fixes #104763). It is mutually dependent on the second change above: an attempt to land it separately in #104746 caused several crater regressions that can all be mitigated by using the implied from the impl header. It is also necessary for the soundness of associated consts that use the implied bounds of impl header. See #104763 and how the third commit fixes the soundness issue in tests/ui/wf/wf-associated-const.rs that was introduces by the previous commit.

cc @lcnr
r? types

jackh726 · 2022-11-07T19:51:45Z

Makes sense to me. We should do a crater run, just to check.

lcnr

This is feels like a step in the right direction. let's run crater and if there aren't any bad regressions we should merge this

compiler/rustc_borrowck/src/type_check/mod.rs

lcnr · 2022-11-09T09:23:46Z

@bors try

lcnr · 2022-11-14T09:35:05Z

this also fixes #84591 (comment), it should not fix the original issue afaict though.

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

lcnr · 2023-02-15T09:58:12Z

@rustbot author

JohnCSimon · 2023-03-17T04:08:16Z

@aliemjay

ping from triage - can you post your status on this PR? There hasn't been an update in a few months. Thanks!

FYI: when a PR is ready for review, send a message containing
@rustbot ready to switch to S-waiting-on-review so the PR is in the reviewer's backlog.

Dylan-DPC · 2023-05-17T10:53:14Z

Closing this as inactive. Feel free to reöpen this pr or create a new pr if you get the time to work on this. Thanks

aliemjay · 2023-11-08T09:31:48Z

Anniversary update is here :)

This now also fixes #104764 and #104763

@rustbot review
@bors try @rust-timer queue

aliemjay · 2023-11-20T12:44:03Z

benchmark after using the TypeOps's fast path for WF obligations.
@bors try @rust-timer queue

bors · 2023-11-20T12:45:16Z

⌛ Trying commit 61bd7f9 with merge 66ac3f1...

fix fn/const items implied bounds and wf check These are two distinct changes (edit: actually three, see below): 1. Wf-check all fn item args. This is a soundness fix. Fixes rust-lang#104005 2. Use implied bounds from impl header in borrowck of associated functions/consts. This strictly accepts more code and helps to mitigate the impact of other breaking changes. Fixes rust-lang#98852 Fixes rust-lang#102611 The first is a breaking change and will likely have a big impact without the the second one. See the first commit for how it breaks libstd. Landing the second one without the first will allow more incorrect code to pass. For example an exploit of rust-lang#104005 would be as simple as: ```rust use core::fmt::Display; trait ExtendLt<Witness> { fn extend(self) -> Box<dyn Display>; } impl<T: Display> ExtendLt<&'static T> for T { fn extend(self) -> Box<dyn Display> { Box::new(self) } } fn main() { let val = (&String::new()).extend(); println!("{val}"); } ``` The third change is to to check WF of user type annotations before normalizing them (fixes rust-lang#104764, fixes rust-lang#104763). It is mutually dependent on the second change above: an attempt to land it separately in rust-lang#104746 caused several crater regressions that can all be mitigated by using the implied from the impl header. It is also necessary for the soundness of associated consts that use the implied bounds of impl header. See rust-lang#104763 and how the third commit fixes the soundness issue in `tests/ui/wf/wf-associated-const.rs` that was introduces by the previous commit. cc `@lcnr` r? types

ghost · 2023-11-20T14:05:58Z

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

+                // We currently add implied bounds from the normalized ty only.
+                // This is more conservative and matches wfcheck behavior.


Suggested change

// We currently add implied bounds from the normalized ty only.

// This is more conservative and matches wfcheck behavior.

// We currently add implied bounds from the normalized `ty` only.

// This is more conservative and matches `wfcheck` behavior.

Markup consistency edits.

bors · 2023-11-20T14:11:55Z

☀️ Try build successful - checks-actions
Build commit: 66ac3f1 (66ac3f183c9d4ebfe29e2c23b49b82ee445529b9)

rust-timer · 2023-11-21T18:17:04Z

Finished benchmarking commit (66ac3f1): comparison URL.

Overall result: ❌ regressions - ACTION NEEDED

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 a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.2%, 0.5%]	25
Regressions ❌ (secondary)	0.8%	[0.1%, 1.4%]	15
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[0.2%, 0.5%]	25

Max RSS (memory usage)

Results

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)	1.0%	[1.0%, 1.0%]	1
Regressions ❌ (secondary)	3.7%	[3.6%, 3.7%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.2%	[-1.4%, -1.0%]	2
All ❌✅ (primary)	1.0%	[1.0%, 1.0%]	1

Cycles

Results

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)	1.7%	[1.4%, 1.9%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.8%	[-1.8%, -1.8%]	1
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 674.774s -> 678.026s (0.48%)
Artifact size: 313.77 MiB -> 313.77 MiB (-0.00%)

rfcbot · 2023-12-04T15:42:07Z

🔔 This is now entering its final comment period, as per the review above. 🔔

…mpiler-errors temporarily revert "ice on ambguity in mir typeck" Reverts rust-lang#116530 as a temporary measure to fix rust-lang#117577. That issue should be ultimately fixed by checking WF of type annotations prior to normalization, which is implemented in rust-lang#104098 but this PR is intended to be backported to beta. r? `@compiler-errors` (the reviewer of the reverted PR)

…mpiler-errors temporarily revert "ice on ambguity in mir typeck" Reverts rust-lang#116530 as a temporary measure to fix rust-lang#117577. That issue should be ultimately fixed by checking WF of type annotations prior to normalization, which is implemented in rust-lang#104098 but this PR is intended to be backported to beta. r? ``@compiler-errors`` (the reviewer of the reverted PR)

Rollup merge of rust-lang#118736 - aliemjay:revert-ice-on-ambig, r=compiler-errors temporarily revert "ice on ambguity in mir typeck" Reverts rust-lang#116530 as a temporary measure to fix rust-lang#117577. That issue should be ultimately fixed by checking WF of type annotations prior to normalization, which is implemented in rust-lang#104098 but this PR is intended to be backported to beta. r? ``@compiler-errors`` (the reviewer of the reverted PR)

rfcbot · 2023-12-14T15:46:46Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

lcnr

r=me after rebase

lcnr · 2024-01-16T08:34:20Z

closing in favor of a rebase of this PR in #120019.

fix fn/const items implied bounds and wf check (rebase) A rebase of rust-lang#104098, see that PR for discussion. This is pretty much entirely the work of `@aliemjay.` I received his permission for this rebase. --- These are two distinct changes (edit: actually three, see below): 1. Wf-check all fn item args. This is a soundness fix. Fixes rust-lang#104005 2. Use implied bounds from impl header in borrowck of associated functions/consts. This strictly accepts more code and helps to mitigate the impact of other breaking changes. Fixes rust-lang#98852 Fixes rust-lang#102611 The first is a breaking change and will likely have a big impact without the the second one. See the first commit for how it breaks libstd. Landing the second one without the first will allow more incorrect code to pass. For example an exploit of rust-lang#104005 would be as simple as: ```rust use core::fmt::Display; trait ExtendLt<Witness> { fn extend(self) -> Box<dyn Display>; } impl<T: Display> ExtendLt<&'static T> for T { fn extend(self) -> Box<dyn Display> { Box::new(self) } } fn main() { let val = (&String::new()).extend(); println!("{val}"); } ``` The third change is to to check WF of user type annotations before normalizing them (fixes rust-lang#104764, fixes rust-lang#104763). It is mutually dependent on the second change above: an attempt to land it separately in rust-lang#104746 caused several crater regressions that can all be mitigated by using the implied from the impl header. It is also necessary for the soundness of associated consts that use the implied bounds of impl header. See rust-lang#104763 and how the third commit fixes the soundness issue in `tests/ui/wf/wf-associated-const.rs` that was introduces by the previous commit. r? types

rustbot assigned lcnr Nov 7, 2022

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aliemjay commented Nov 23, 2022

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aliemjay mentioned this pull request Aug 15, 2023

function type params are not checked for well-formedness #104005

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rust-cloud-vms bot force-pushed the fn-wf branch from 93db656 to cc24527 Compare November 8, 2023 09:22

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temporarily revert "ice on ambguity in mir typeck" #118736

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Check normalized call signature for WF in mir typeck #118882

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fix fn/const items implied bounds and wf check (rebase) #120019

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fix fn/const items implied bounds and wf check #104098

fix fn/const items implied bounds and wf check #104098

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		// We currently add implied bounds from the normalized ty only.
		// This is more conservative and matches wfcheck behavior.

fix fn/const items implied bounds and wf check #104098

fix fn/const items implied bounds and wf check #104098

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Overall result: ❌ regressions - ACTION NEEDED

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