Tait must be constrained if in sig #113169

oli-obk · 2023-06-29T19:43:12Z

kind of reverts #62423, but that PR only removed cycles in cases that we want to forbid now anyway.

see https://rust-lang.zulipchat.com/#narrow/stream/315482-t-compiler.2Fetc.2Fopaque-types/topic/lcnr.20oli.20meeting/near/370712246 for related discussion and motivating example

a TAIT showing up in a signature doesn't just mean it can register a hidden type, but that it must.

This is the design the types team decided upon for the following reasons

avoids a hypothetical situation where getting smarter in trait solving could cause new cycle errors or new inference errors to show up, where today something is treated as opaque.
avoids having the situation where a (minor?) change to a function body causes an error, because its TAIT usage suddenly isn't "opaque enough" anymore.
avoids having to explain why in some cases you need to put a Tait into a tiny module together with its defining usages. Now you basically gotta always do this, the moment a Tait is in a signature that isn't in the defining scope.
avoids false-cycle errors
anything diverging from this pattern needs to either
- move the TAIT declaration and defining function into their own helper sub module
- use the attributes we'll provide in the future to explicitly opt in or out of being in the defining scope

fixes #117861

reverts #125362 cc @Nilstrieb @joboet

rustbot · 2023-06-29T19:43:17Z

rustc_error_messages was changed

cc @davidtwco, @compiler-errors, @JohnTitor, @TaKO8Ki

oli-obk · 2023-06-29T19:46:47Z

tests/ui/type-alias-impl-trait/issue-63355.rs

@@ -1,5 +1,4 @@
 #![feature(type_alias_impl_trait)]
-// check-pass


This is the only test for which there was no workaround after this change.

bors · 2023-07-05T19:35:40Z

☔ The latest upstream changes (presumably #113370) made this pull request unmergeable. Please resolve the merge conflicts.

oli-obk · 2023-10-24T15:52:04Z

tests/ui/type-alias-impl-trait/type-alias-impl-trait-fns.rs

-// check-pass
-


This PR "reopens" #61863

the test doesn't really add too much new test coverage compared with other tests we already have.

bors · 2023-10-25T11:58:34Z

☔ The latest upstream changes (presumably #117076) made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2023-10-25T20:25:20Z

☔ The latest upstream changes (presumably #117172) made this pull request unmergeable. Please resolve the merge conflicts.

rustbot · 2023-10-26T06:56:20Z

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

oli-obk · 2023-10-30T16:21:27Z

@rustbot ready

…in a hidden type

…ped in a `fn main() {}` body

oli-obk · 2024-06-12T08:54:53Z

@bors r=lcnr

bors · 2024-06-12T08:54:56Z

📌 Commit 85f2eca has been approved by lcnr

It is now in the queue for this repository.

bors · 2024-06-12T09:00:41Z

⌛ Testing commit 85f2eca with merge 02c7a59...

bors · 2024-06-12T11:09:42Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 02c7a59 to master...

rust-timer · 2024-06-12T12:45:22Z

Finished benchmarking commit (02c7a59): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

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

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)	0.7%	[0.7%, 0.7%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.3%	[-0.4%, -0.3%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.0%	[-0.4%, 0.7%]	3

Max RSS (memory usage)

Results (primary 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)	5.2%	[2.3%, 8.1%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-4.3%	[-5.9%, -2.7%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[-5.9%, 8.1%]	4

Cycles

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

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)	0.1%	[0.0%, 0.5%]	8
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.0%]	5
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[-0.1%, 0.5%]	13

Bootstrap: 675.824s -> 676.122s (0.04%)
Artifact size: 320.07 MiB -> 320.07 MiB (0.00%)

lqd · 2024-06-12T12:48:51Z

Probably noise + we need the fix => @rustbot label: +perf-regression-triaged

…r-errors Test that opaque types can't have themselves as a hidden type with incompatible lifetimes fixes rust-lang#122876 This PR used to add extra logic to prevent those cases, but after rust-lang#113169 this is implicitly rejected, because such usages are not defining.

Rollup merge of rust-lang#123782 - oli-obk:equal_tait_args, r=compiler-errors Test that opaque types can't have themselves as a hidden type with incompatible lifetimes fixes rust-lang#122876 This PR used to add extra logic to prevent those cases, but after rust-lang#113169 this is implicitly rejected, because such usages are not defining.

rust-lang/rust#113169 Signed-off-by: xxchan <[email protected]>

oli-obk commented Jun 29, 2023

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apiraino removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 12, 2023

oli-obk reopened this Oct 24, 2023

oli-obk force-pushed the tait_must_be_constrained_if_in_sig branch 2 times, most recently from b6612f4 to 62d2ddd Compare October 24, 2023 13:12

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oli-obk force-pushed the tait_must_be_constrained_if_in_sig branch from 62d2ddd to 64f3f5b Compare October 24, 2023 13:36

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bors added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Oct 25, 2023

oli-obk force-pushed the tait_must_be_constrained_if_in_sig branch from 64f3f5b to fd06ad3 Compare October 25, 2023 13:04

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oli-obk force-pushed the tait_must_be_constrained_if_in_sig branch from fd06ad3 to d9b265f Compare October 25, 2023 13:45

oli-obk mentioned this pull request Oct 25, 2023

Pessimistically assume opaque types are !Freeze #113617

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oli-obk force-pushed the tait_must_be_constrained_if_in_sig branch from f0a4804 to 1d5ea10 Compare October 26, 2023 06:56

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Oct 30, 2023

oli-obk added 2 commits June 12, 2024 08:53

Require any function with a tait in its signature to actually constra…

0bc2001

…in a hidden type

Add a fn main() {} to a doctest to prevent the test from being wrap…

85f2eca

…ped in a `fn main() {}` body

oli-obk force-pushed the tait_must_be_constrained_if_in_sig branch from a54797c to 85f2eca Compare June 12, 2024 08:54

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 Jun 12, 2024

bors added the merged-by-bors This PR was explicitly merged by bors. label Jun 12, 2024

bors merged commit 02c7a59 into rust-lang:master Jun 12, 2024
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rustbot added this to the 1.81.0 milestone Jun 12, 2024

bors mentioned this pull request Jun 12, 2024

Treat weak alias types more like ADTs when computing implied bounds #122340

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rustbot added the perf-regression Performance regression. label Jun 12, 2024

oli-obk deleted the tait_must_be_constrained_if_in_sig branch June 12, 2024 12:46

rustbot added the perf-regression-triaged The performance regression has been triaged. label Jun 12, 2024

lqd mentioned this pull request Jun 13, 2024

TAIT feature is broken #126387

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Dirbaio mentioned this pull request Jun 18, 2024

macro expansion broken on latest nightly (2024-06-13) embassy-rs/embassy#3078

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oli-obk mentioned this pull request Jun 18, 2024

Test that opaque types can't have themselves as a hidden type with incompatible lifetimes #123782

Merged

xxchan added a commit to risingwavelabs/risingwave that referenced this pull request Jun 20, 2024

downgrade due to TAIT

1b95f15

rust-lang/rust#113169 Signed-off-by: xxchan <[email protected]>

xxchan mentioned this pull request Jul 11, 2024

build: bump toolchain to 2024-06-12 risingwavelabs/risingwave#17179

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rrauch mentioned this pull request Aug 21, 2024

Fix Compilation Errors, Add Stable Rust Support, Improve Compatibility, and Implement Futures::io Traits alvra/reqwest-file#4

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Tait must be constrained if in sig #113169

Tait must be constrained if in sig #113169

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lqd commented Jun 12, 2024

		@@ -1,5 +1,4 @@
		#![feature(type_alias_impl_trait)]
		// check-pass

Tait must be constrained if in sig #113169

Tait must be constrained if in sig #113169

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Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Instruction count

Max RSS (memory usage)

Cycles

Binary size

lqd commented Jun 12, 2024

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