[experiment][2] meow mrrrumph by WaffleLapkin · Pull Request #155501 · rust-lang/rust

WaffleLapkin · 2026-04-18T22:16:30Z

No description provided.

WaffleLapkin · 2026-04-18T22:23:47Z

…<try> [experiment][2] meow mrrrumph

rust-bors · 2026-04-19T00:32:54Z

☀️ Try build successful (CI)
Build commit: 5ec4d3b (5ec4d3b0c83717313176eefa7d71e9d36dc83355, parent: b2f1ccf524a3a4cf9c34545167cc23b659cf1cbd)

??? why wasn't this detected by compiletest ???

craterbot · 2026-04-19T01:22:15Z

👌 Experiment pr-155501 created and queued.
🤖 Automatically detected try build 5ec4d3b
⚠️ Try build based on commit e92338e, but latest commit is 8fdb420. Did you forget to make a new try build?
🔍 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

craterbot · 2026-04-20T13:39:31Z

🚧 Experiment pr-155501 is now running

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

craterbot · 2026-04-20T18:15:46Z

🎉 Experiment pr-155501 is completed!
📊 3232 regressed and 0 fixed (9024 total)
📊 1201 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary 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

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-155501/retry-regressed-list.txt ↩

WaffleLapkin · 2026-04-21T11:29:39Z

@craterbot check p=1 name=155501-infallible-never-no-reservation start=try#1c4199da70f816f2239f41c55168ff75a3663718 end=try#5ec4d3b0c83717313176eefa7d71e9d36dc83355 crates=https://crater-reports.s3.amazonaws.com/pr-154887/retry-regressed-list.txt

Failures of this PR, on top of #155499 (i.e. what is broken by making infallible never without the reservation impl)

craterbot · 2026-04-21T11:29:44Z

👌 Experiment 155501-infallible-never-no-reservation created and queued.
🔍 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-bors · 2026-04-23T12:54:15Z

☔ The latest upstream changes (presumably #155674) made this pull request unmergeable. Please resolve the merge conflicts.

craterbot · 2026-04-27T04:04:32Z

🚧 Experiment 155501-infallible-never-no-reservation is now running

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

craterbot · 2026-04-27T07:04:16Z

🎉 Experiment 155501-infallible-never-no-reservation is completed!
📊 81 regressed and 0 fixed (9025 total)
📊 916 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary 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

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/155501-infallible-never-no-reservation/retry-regressed-list.txt ↩

… r=JonathanBrouwer stabilize never type ### This PR - stabilizes the [never type](https://doc.rust-lang.org/stable/std/primitive.never.html) (aka `!`) (!!!) - sets the [never type fallback](https://doc.rust-lang.org/edition-guide/rust-2024/never-type-fallback.html) to `!` on all editions (breaking change, see [crater report analysis](rust-lang#155499 (comment)) and [refresher on never type fallback](rust-lang#155499 (comment))) - makes `Infallible` an alias to `!` - removes `dependency_on_unit_never_type_fallback` lint (there is no more never type fallback to `()` so this lint can't be triggered) ### Cat <img width="1024" height="683" alt="52270233795_5979a3174d_b" src="https://github.com/user-attachments/assets/f6b4737e-32ef-4c33-86b2-76b81673cf20" /> ### Tracking - rust-lang#35121 - rust-lang#148922 ### FCPs - rust-lang#123508 (comment) (stabilization plan, T-lang) - rust-lang#155499 (comment) (never type stabilization modulo bugs, T-lang) - rust-lang#155924 (comment) (make `Infallible = !`, T-libs) ### Related changes - Lint bump: rust-lang#141937 - Rust 2024 edition change: - rust-lang#123748 - rust-lang#123508 - Various changes to lessen the effect of the breaking changes: - rust-lang#157820 - rust-lang#156047 - rust-lang#160705 - Never type documentation changes: rust-lang#158370 (blocked on this pr) ### Experiments - Fallback change and never type stabilization: - Run: rust-lang#155499 (comment) - Analysis: rust-lang#155499 (comment) - Status of backports: rust-lang#155499 (comment) - Fallback change, never type stabilization and making `Infallible = !`: rust-lang#155500 - Fallback change, never type stabilization, making `Infallible = !`, and removing reservation impl: rust-lang#155501 - Never type stabilization and `Infallible = !` change, _without_ fallback change: rust-lang#155657 --- Closes rust-lang#35121 Closes rust-lang#148922

…Brouwer stabilize never type ### This PR - stabilizes the [never type](https://doc.rust-lang.org/stable/std/primitive.never.html) (aka `!`) (!!!) - sets the [never type fallback](https://doc.rust-lang.org/edition-guide/rust-2024/never-type-fallback.html) to `!` on all editions (breaking change, see [crater report analysis](#155499 (comment)) and [refresher on never type fallback](#155499 (comment))) - makes `Infallible` an alias to `!` - removes `dependency_on_unit_never_type_fallback` lint (there is no more never type fallback to `()` so this lint can't be triggered) ### Cat <img width="1024" height="683" alt="52270233795_5979a3174d_b" src="https://github.com/user-attachments/assets/f6b4737e-32ef-4c33-86b2-76b81673cf20" /> ### Tracking - #35121 - #148922 ### FCPs - #123508 (comment) (stabilization plan, T-lang) - #155499 (comment) (never type stabilization modulo bugs, T-lang) - #155924 (comment) (make `Infallible = !`, T-libs) ### Related changes - Lint bump: #141937 - Rust 2024 edition change: - #123748 - #123508 - Various changes to lessen the effect of the breaking changes: - #157820 - #156047 - #160705 - Never type documentation changes: #158370 (blocked on this pr) ### Experiments - Fallback change and never type stabilization: - Run: #155499 (comment) - Analysis: #155499 (comment) - Status of backports: #155499 (comment) - Fallback change, never type stabilization and making `Infallible = !`: #155500 - Fallback change, never type stabilization, making `Infallible = !`, and removing reservation impl: #155501 - Never type stabilization and `Infallible = !` change, _without_ fallback change: #155657 --- Closes #35121 Closes #148922

… r=JonathanBrouwer stabilize never type ### This PR - stabilizes the [never type](https://doc.rust-lang.org/stable/std/primitive.never.html) (aka `!`) (!!!) - sets the [never type fallback](https://doc.rust-lang.org/edition-guide/rust-2024/never-type-fallback.html) to `!` on all editions (breaking change, see [crater report analysis](rust-lang#155499 (comment)) and [refresher on never type fallback](rust-lang#155499 (comment))) - makes `Infallible` an alias to `!` - removes `dependency_on_unit_never_type_fallback` lint (there is no more never type fallback to `()` so this lint can't be triggered) ### Cat <img width="1024" height="683" alt="52270233795_5979a3174d_b" src="https://github.com/user-attachments/assets/f6b4737e-32ef-4c33-86b2-76b81673cf20" /> ### Tracking - rust-lang#35121 - rust-lang#148922 ### FCPs - rust-lang#123508 (comment) (stabilization plan, T-lang) - rust-lang#155499 (comment) (never type stabilization modulo bugs, T-lang) - rust-lang#155924 (comment) (make `Infallible = !`, T-libs) ### Related changes - Lint bump: rust-lang#141937 - Rust 2024 edition change: - rust-lang#123748 - rust-lang#123508 - Various changes to lessen the effect of the breaking changes: - rust-lang#157820 - rust-lang#156047 - rust-lang#160705 - Never type documentation changes: rust-lang#158370 (blocked on this pr) ### Experiments - Fallback change and never type stabilization: - Run: rust-lang#155499 (comment) - Analysis: rust-lang#155499 (comment) - Status of backports: rust-lang#155499 (comment) - Fallback change, never type stabilization and making `Infallible = !`: rust-lang#155500 - Fallback change, never type stabilization, making `Infallible = !`, and removing reservation impl: rust-lang#155501 - Never type stabilization and `Infallible = !` change, _without_ fallback change: rust-lang#155657 --- Closes rust-lang#35121 Closes rust-lang#148922

…Brouwer stabilize never type ### This PR - stabilizes the [never type](https://doc.rust-lang.org/stable/std/primitive.never.html) (aka `!`) (!!!) - sets the [never type fallback](https://doc.rust-lang.org/edition-guide/rust-2024/never-type-fallback.html) to `!` on all editions (breaking change, see [crater report analysis](#155499 (comment)) and [refresher on never type fallback](#155499 (comment))) - makes `Infallible` an alias to `!` - removes `dependency_on_unit_never_type_fallback` lint (there is no more never type fallback to `()` so this lint can't be triggered) ### Cat <img width="1024" height="683" alt="52270233795_5979a3174d_b" src="https://github.com/user-attachments/assets/f6b4737e-32ef-4c33-86b2-76b81673cf20" /> ### Tracking - #35121 - #148922 ### FCPs - #123508 (comment) (stabilization plan, T-lang) - #155499 (comment) (never type stabilization modulo bugs, T-lang) - #155924 (comment) (make `Infallible = !`, T-libs) ### Related changes - Lint bump: #141937 - Rust 2024 edition change: - #123748 - #123508 - Various changes to lessen the effect of the breaking changes: - #157820 - #156047 - #160705 - Never type documentation changes: #158370 (blocked on this pr) ### Experiments - Fallback change and never type stabilization: - Run: #155499 (comment) - Analysis: #155499 (comment) - Status of backports: #155499 (comment) - Fallback change, never type stabilization and making `Infallible = !`: #155500 - Fallback change, never type stabilization, making `Infallible = !`, and removing reservation impl: #155501 - Never type stabilization and `Infallible = !` change, _without_ fallback change: #155657 --- Closes #35121 Closes #148922

WaffleLapkin added 6 commits April 18, 2026 23:18

Set never type fallback to always be !

d834459

stabilize the never type (!)

b63a1a4

fixup clippy::empty_enums

1b7c97d

remove #![feature(never_type)] from the compiler

bdacd4f

remove #![feature(never_type)] from tests

28949e1

remove #![feature(never_type)] from library

0eb0e6d

This comment has been minimized.

Sign in to view

rust-bors Bot pushed a commit that referenced this pull request Apr 18, 2026

Auto merge of #155501 - WaffleLapkin:dont-reserve-from-never-type, r=…

5ec4d3b

…<try> [experiment][2] meow mrrrumph

WaffleLapkin added 10 commits April 19, 2026 03:03

remove #![feature(never_type)] from tools

328663d

bless tests

5f0be1e

bless mir-opt tests

01d239b

update tests which depended on never fallback to ()

bb3e31c

change never type fallback in r-a

5cf8e18

remove dependency_on_unit_never_type_fallback lint

293fa75

remove stray stderr files

c374e4d

??? why wasn't this detected by compiletest ???

TMP: allow a lint in r-a

aebed0c

update edition-guide submodule to unfuck tests there

3e8df8d

Make Infallible = !

474cf60

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 19, 2026

This comment was marked as off-topic.

Sign in to view

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Apr 20, 2026

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 21, 2026

WaffleLapkin mentioned this pull request Apr 21, 2026

[experiment][1] mew #155500

Closed

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Apr 27, 2026

WaffleLapkin mentioned this pull request Apr 28, 2026

Make Infallible = ! #155924

Open

WaffleLapkin added S-experimental Status: Ongoing experiment that does not require reviewing and won't be merged in its current state. F-never_type `#![feature(never_type)]` and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 14, 2026

WaffleLapkin closed this Jul 10, 2026

WaffleLapkin mentioned this pull request Aug 14, 2026

stabilize never type #155499

Merged

Navigation Menu

Uh oh!

Uh oh!

[experiment][2] meow mrrrumph - #155501

[experiment][2] meow mrrrumph#155501
WaffleLapkin wants to merge 19 commits into
rust-lang:mainfrom
WaffleLapkin:dont-reserve-from-never-type

WaffleLapkin commented Apr 18, 2026

Uh oh!

WaffleLapkin commented Apr 18, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented Apr 19, 2026

Uh oh!

craterbot commented Apr 19, 2026

Uh oh!

This comment was marked as off-topic.

craterbot commented Apr 20, 2026

Uh oh!

craterbot commented Apr 20, 2026

Uh oh!

WaffleLapkin commented Apr 21, 2026

Uh oh!

craterbot commented Apr 21, 2026

Uh oh!

rust-bors Bot commented Apr 23, 2026

Uh oh!

craterbot commented Apr 27, 2026

Uh oh!

craterbot commented Apr 27, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Uh oh!

Uh oh!

Conversation

WaffleLapkin commented Apr 18, 2026

Uh oh!

WaffleLapkin commented Apr 18, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented Apr 19, 2026

Uh oh!

craterbot commented Apr 19, 2026

Uh oh!

This comment was marked as off-topic.

craterbot commented Apr 20, 2026

Uh oh!

craterbot commented Apr 20, 2026

Footnotes

Uh oh!

WaffleLapkin commented Apr 21, 2026

Uh oh!

craterbot commented Apr 21, 2026

Uh oh!

rust-bors Bot commented Apr 23, 2026

Uh oh!

craterbot commented Apr 27, 2026

Uh oh!

craterbot commented Apr 27, 2026

Footnotes

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants