Document never type fallback in `!`'s docs#124419

WaffleLapkin · 2024-04-26T18:51:26Z

Pulled the documentation I've written for #123939.

I want a single place where never type fallback is explained, which can be referred in all the lints and migration materials.

rustbot · 2024-04-26T18:51:34Z

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workingjubilee

Thanks! Some minor clarity-related nits. Overall looks good to me.

library/core/src/primitive_docs.rs

Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>

workingjubilee · 2024-04-26T23:52:08Z

nice!

@bors r+ rollup

bors · 2024-04-26T23:52:11Z

📌 Commit b73bfd2 has been approved by workingjubilee

It is now in the queue for this repository.

library/core/src/primitive_docs.rs

kpreid · 2024-04-26T23:49:23Z

library/core/src/primitive_docs.rs

+/// To prevent such errors, the compiler remembers where it inserted `absurd` calls, and
+/// if it can't infer their type, it sets the type to the fallback type:
+/// ```rust, ignore
+/// type Fallback = /* An arbitrarily selected type! */;


"Arbitrarily selected" here sounds like "the compiler picks from some set", not "we made a choice and taught it to the compiler". I'm not sure what would be better, though.

There's nothing stopping us from having arbitrarily complicated fallback logic, aside from a reluctance to implement anything more complex, which is why I suggested it that way.

We do pick from a set.

The set has one member. :^)

Hoping to grow the set to two :p

I'm also not a fan of "arbitrary" here because we did purposefully choose the fallback type...

But I'm not sure how to phrase this properly :/

Whenever I use arbitrary I strongly mean the "the reason for why is because I said so", because often there were multiple reasonable choices we could have made, but we could only make one (one set, with any number of members).

library/core/src/primitive_docs.rs

WaffleLapkin · 2024-04-26T23:57:35Z

@bors r-
(so that I can apply @kpreid suggestions)

library/core/src/primitive_docs.rs

Co-authored-by: Kevin Reid <kpreid@switchb.org> Co-authored-by: Herman Skogseth <herman.skogseth@me.com> Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>

WaffleLapkin · 2024-05-02T02:21:15Z

Thanks to everyone who participated in the discussions and suggested improvements to the documentation! <3

@bors r=workingjubilee

bors · 2024-05-02T02:21:18Z

📌 Commit e2eb053 has been approved by workingjubilee

It is now in the queue for this repository.

library/core/src/primitive_docs.rs

Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>

workingjubilee · 2024-05-02T04:25:02Z

@bors r+

bors · 2024-05-02T04:25:05Z

📌 Commit e18b6e8 has been approved by workingjubilee

It is now in the queue for this repository.

bors · 2024-05-02T11:54:56Z

⌛ Testing commit e18b6e8 with merge 80451a4...

bors · 2024-05-02T13:57:14Z

☀️ Test successful - checks-actions
Approved by: workingjubilee
Pushing 80451a4 to master...

rust-timer · 2024-05-02T16:08:10Z

Finished benchmarking commit (80451a4): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

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	mean	range	count
Regressions ❌ (primary)	1.2%	[1.2%, 1.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.1%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[-0.1%, 1.2%]	2

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Bootstrap: 675.937s -> 674.735s (-0.18%)
Artifact size: 315.99 MiB -> 316.01 MiB (0.01%)

Document never type fallback in !'s docs

23b67de

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Tracking Issue for Rust 2024: Make ! fall back to ! #123748

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b73bfd2

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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-review Status: Awaiting review from the assignee but also interested parties. labels Apr 26, 2024

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Co-authored-by: Kevin Reid <kpreid@switchb.org> Co-authored-by: Herman Skogseth <herman.skogseth@me.com> Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>

Slightly reformat !'s docs after applying github suggestions

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fixup links in never type docs

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bors merged commit 80451a4 into rust-lang:master May 2, 2024

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WaffleLapkin deleted the never-type-fallback-docs branch May 2, 2024 19:51

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