More robustly deal with relaxed bounds and improve their diagnostics #142693

fmease · 2025-06-18T20:23:53Z

Scaffolding for #135229 (CC #135331)

Fixes #136944 (6th commit).
Fixes #142718 (8th commit).

fmease · 2025-06-20T21:20:38Z

@bors2 try @rust-timer queue

rust-bors · 2025-06-20T21:20:42Z

⌛ Trying commit 04dad4e with merge bfa10de…

To cancel the try build, run the command @bors2 try cancel.

More robustly deal with relaxed bounds and improve their diagnostics Scaffolding for #135229 (CC #135331) Fixes #136944. Fixes #142718.

rust-bors · 2025-06-20T23:49:40Z

☀️ Try build successful (CI)
Build commit: bfa10de (bfa10de6407128926b18c60d51c9f19df73e336c, parent: 9c4ff566babe632af5e30281a822d1ae9972873b)

rust-timer · 2025-06-21T02:22:46Z

Finished benchmarking commit (bfa10de): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

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

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	3.0%	[3.0%, 3.0%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.0%	[3.0%, 3.0%]	1

Max RSS (memory usage)

Results (secondary -2.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.4%	[2.4%, 2.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.5%	[-5.8%, -1.8%]	6
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 2.9%, secondary 4.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.9%	[2.9%, 2.9%]	1
Regressions ❌ (secondary)	4.4%	[2.8%, 7.6%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.9%	[2.9%, 2.9%]	1

Binary size

Results (primary 1.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.1%	[1.1%, 1.1%]	1

Bootstrap: 692.606s -> 692.191s (-0.06%)
Artifact size: 372.01 MiB -> 371.99 MiB (-0.01%)

bors · 2025-06-27T20:17:23Z

☔ The latest upstream changes (presumably #143091) made this pull request unmergeable. Please resolve the merge conflicts.

fmease · 2025-06-27T22:56:30Z

#142693 (comment)

Looks spurious?

* The phrasing "only does something for" made sense back when this diagnostic was a (hard) warning. Now however, it's simply a hard error and thus completely rules out "doing something". * The primary message was way too long * The new wording more closely mirrors the wording we use for applying other bound modifiers (like `const` and `async`) to incompatible traits. * "all other traits are not bound by default" is no longer accurate under Sized Hierarchy. E.g., traits and assoc tys are (currently) bounded by `MetaSized` by default but can't be relaxed using `?MetaSized` (instead, you relax it by adding `PointeeSized`). * I've decided against adding any diagnositic notes or suggestions for now like "trait `Trait` can't be relaxed as it's not bound by default" which would be incorrect for `MetaSized` and assoc tys as mentioned above) or "consider changing `?MetaSized` to `PointeeSized`" as the Sized Hierarchy impl is still WIP)

Having multiple relaxed bounds like `?Sized + ?Iterator` is actually *fine*. We actually want to reject *duplicate* relaxed bounds like `?Sized + ?Sized` because these most certainly represent a user error. Note that this doesn't mean that we accept more code because a bound like `?Iterator` is still invalid as it's not relaxing a *default* trait and the only way to define / use more default bounds is under the experimental and internal feature `more_maybe_bounds` plus `lang_items` plus unstable flag `-Zexperimental-default-bounds` (historical context: for the longest time, bounds like `?Iterator` were actually allowed and lead to a hard warning). Ultimately, this simply *reframes* the diagnostic. The scope of `more_maybe_bounds` / `-Zexperimental-default-bounds` remains unchanged as well.

fmease · 2025-07-18T10:30:22Z

(lol I should've just built the compiler for the rebase instead of doing a CI-directed one, that was painful, thanks tired me doing a night shift)

Rebased, added some more (doc) comments and got rid of the more_maybe_bounds advertisement (didn't do it as a follow-up so I can already use this as a good base branch for #135331.

@bors r=compiler-errors

bors · 2025-07-18T10:30:25Z

📌 Commit 82a02ae has been approved by compiler-errors

It is now in the queue for this repository.

fmease · 2025-07-18T10:32:02Z

@bors rollup- alleviate pressure

…er-errors More robustly deal with relaxed bounds and improve their diagnostics Scaffolding for rust-lang#135229 (CC rust-lang#135331) Fixes rust-lang#136944 (6th commit). Fixes rust-lang#142718 (8th commit).

Rollup of 9 pull requests Successful merges: - #138554 (Distinguish delim kind to decide whether to emit unexpected closing delimiter) - #142673 (Show the offset, length and memory of uninit read errors) - #142693 (More robustly deal with relaxed bounds and improve their diagnostics) - #143382 (stabilize `const_slice_reverse`) - #143928 (opt-dist: make llvm builds optional) - #143961 (Correct which exploit mitigations are enabled by default) - #144050 (Fix encoding of link_section and no_mangle cross crate) - #144059 (Refactor `CrateLoader` into the `CStore`) - #144123 (Generalize `unsize` and `unsize_into` destinations) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #142693 - fmease:unbound-bettering, r=compiler-errors More robustly deal with relaxed bounds and improve their diagnostics Scaffolding for #135229 (CC #135331) Fixes #136944 (6th commit). Fixes #142718 (8th commit).

Rollup of 9 pull requests Successful merges: - rust-lang/rust#138554 (Distinguish delim kind to decide whether to emit unexpected closing delimiter) - rust-lang/rust#142673 (Show the offset, length and memory of uninit read errors) - rust-lang/rust#142693 (More robustly deal with relaxed bounds and improve their diagnostics) - rust-lang/rust#143382 (stabilize `const_slice_reverse`) - rust-lang/rust#143928 (opt-dist: make llvm builds optional) - rust-lang/rust#143961 (Correct which exploit mitigations are enabled by default) - rust-lang/rust#144050 (Fix encoding of link_section and no_mangle cross crate) - rust-lang/rust#144059 (Refactor `CrateLoader` into the `CStore`) - rust-lang/rust#144123 (Generalize `unsize` and `unsize_into` destinations) r? `@ghost` `@rustbot` modify labels: rollup

…er-errors More robustly deal with relaxed bounds and improve their diagnostics Scaffolding for rust-lang#135229 (CC rust-lang#135331) Fixes rust-lang#136944 (6th commit). Fixes rust-lang#142718 (8th commit).

…iaskrgr Rollup of 9 pull requests Successful merges: - rust-lang#138554 (Distinguish delim kind to decide whether to emit unexpected closing delimiter) - rust-lang#142673 (Show the offset, length and memory of uninit read errors) - rust-lang#142693 (More robustly deal with relaxed bounds and improve their diagnostics) - rust-lang#143382 (stabilize `const_slice_reverse`) - rust-lang#143928 (opt-dist: make llvm builds optional) - rust-lang#143961 (Correct which exploit mitigations are enabled by default) - rust-lang#144050 (Fix encoding of link_section and no_mangle cross crate) - rust-lang#144059 (Refactor `CrateLoader` into the `CStore`) - rust-lang#144123 (Generalize `unsize` and `unsize_into` destinations) r? `@ghost` `@rustbot` modify labels: rollup

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Jun 18, 2025

fmease force-pushed the unbound-bettering branch from 8d31700 to 4634541 Compare June 18, 2025 20:27

fmease changed the title ~~[WIP] unbound bettering (refactoring)~~ [WIP] unbound bettering Jun 18, 2025

fmease force-pushed the unbound-bettering branch 2 times, most recently from 69e237d to 03d01fa Compare June 19, 2025 02:46

fmease added the rla-silenced Silences rust-log-analyzer postings to the PR it's added on. label Jun 19, 2025

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fmease mentioned this pull request Jun 19, 2025

Sized hierarchy: PointeeSized bounds aren't fully validated during HIR ty lowering #142718

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fmease force-pushed the unbound-bettering branch 3 times, most recently from 8a6f65d to 04dad4e Compare June 20, 2025 21:17

fmease changed the title ~~[WIP] unbound bettering~~ More robustly deal with relaxed bounds and improve their diagnostics Jun 20, 2025

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rust-bors bot added a commit that referenced this pull request Jun 20, 2025

Auto merge of #142693 - fmease:unbound-bettering, r=<try>

bfa10de

More robustly deal with relaxed bounds and improve their diagnostics Scaffolding for #135229 (CC #135331) Fixes #136944. Fixes #142718.

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 20, 2025

fmease mentioned this pull request Jun 20, 2025

Rehome tests in tests/ui/ to accurate subdirectories #142808

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Jun 21, 2025

bors added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jun 27, 2025

fmease mentioned this pull request Jun 27, 2025

We don't fully validate relaxed trait bounds on the RHS of trait aliases (should we actually reject them outright?) #143122

Open

fmease force-pushed the unbound-bettering branch 2 times, most recently from eb7b67e to 94a6965 Compare July 18, 2025 03:07

fmease added 4 commits July 18, 2025 12:13

Reword diagnostics about relaxed bounds in invalid contexts

84ed70b

HIR ty lowering: Validate PointeeSized bounds

82a02ae

fmease force-pushed the unbound-bettering branch from 94a6965 to 82a02ae Compare July 18, 2025 10:25

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 18, 2025

fmease mentioned this pull request Jul 18, 2025

Reject relaxed bounds inside associated type bounds (ATB) #135331

Merged

fmease removed the rla-silenced Silences rust-log-analyzer postings to the PR it's added on. label Jul 18, 2025

This was referenced Jul 18, 2025

Rollup of 10 pull requests #144138

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Rollup of 9 pull requests #144145

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bors merged commit f38891e into rust-lang:master Jul 19, 2025
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rustbot added this to the 1.90.0 milestone Jul 19, 2025

fmease deleted the unbound-bettering branch July 19, 2025 10:07

matthiaskrgr mentioned this pull request Jul 21, 2025

ICE: dyn !Sized #144241

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davidtwco mentioned this pull request Jul 24, 2025

Tracking Issue for Sized Hierarchy #144404

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fmease mentioned this pull request Aug 26, 2025

default auto traits: use default supertraits instead of Self: Trait bounds on associated items #145879

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More robustly deal with relaxed bounds and improve their diagnostics #142693

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Overall result: ❌ regressions - please read the text below

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