Add long description and test for E0311 #100747

MatthewPeterKelly · 2022-08-19T10:48:17Z

Adds a long description and unit test for the E0311 compiler error.

Fixes one line-item in #61137.

Adds a long description and unit test for the E0311 compiler error.

rustbot · 2022-08-19T10:48:20Z

Some changes occurred in diagnostic error codes

rust-highfive · 2022-08-19T10:48:20Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @fee1-dead (or someone else) soon.

Please see the contribution instructions for more information.

compiler/rustc_error_codes/src/error_codes/E0311.md

fee1-dead · 2022-08-19T12:41:37Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+E0311 occurs when there is insufficient information for the rust compiler to
+prove that some time has a long enough lifetime.


Thank you for the contributions! This explanation could be a bit confusing, I don't know how it should be reworded into, cc @compiler-errors any ideas?

Good point -- it would be great to have a better description here. I'm still pretty new to rust, so this was my initial attempt at reverse engineering why the fix worked.

compiler/rustc_error_codes/src/error_codes/E0311.md

Co-authored-by: Guillaume Gomez <[email protected]>

MatthewPeterKelly

Thanks for the quick review. I applied your suggestions and we can wait to see if we get an improved description of the error message from the compiler team.

MatthewPeterKelly · 2022-08-19T13:33:24Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+E0311 occurs when there is insufficient information for the rust compiler to
+prove that some time has a long enough lifetime.


Good point -- it would be great to have a better description here. I'm still pretty new to rust, so this was my initial attempt at reverse engineering why the fix worked.

fee1-dead

I'm okay with the current description with the suggestions applied. A more accurate description could be a followup.

fee1-dead · 2022-08-23T00:50:25Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+
+In this example we have a trait that borrows some inner data element of type `V`
+from an outer type `T`, through an intermediate type `U`. The compiler is unable
+to prove that the livetime of `U` is long enough to support the reference. To


Suggested change

to prove that the livetime of `U` is long enough to support the reference. To

to prove that the lifetime of `U` is long enough to support the reference. To

fee1-dead · 2022-08-23T00:50:29Z

compiler/rustc_error_codes/src/error_codes/E0311.md

@@ -0,0 +1,49 @@
+This error occurs when there is insufficient information for the rust compiler
+to prove that some time has a long enough lifetime.


Suggested change

to prove that some time has a long enough lifetime.

to prove that a type has a long enough lifetime.

MatthewPeterKelly · 2022-08-23T09:44:46Z

This explanation could be a bit confusing, I don't know how it should be reworded into, cc @compiler-errors any ideas?

I made an attempt at improving the description for the E0311.md error message example, based on reading the relevant chapter in the rust book again. The updated description includes some more details about lifetimes and lifetime elision rules, and how they apply to this specific example. There are still some minor details to clean-up (I've added in-line comments to the PR) out, but I think it is getting closer to something that should provide more useful context to a user. I can make another pass at cleaning up the details in the next few days.

fee1-dead · 2022-08-23T11:16:02Z

Let's do a rotation and find another reviewer who might have a better idea for the documentation :)

r? rust-lang/compiler

lcnr · 2022-08-24T07:24:08Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+This error occurs when there is insufficient information for the rust compiler
+to prove that a type has a long enough lifetime.


Suggested change

This error occurs when there is insufficient information for the rust compiler

to prove that a type has a long enough lifetime.

This error occurs when there is an unsatisfied outlives bound on a generic type parameter or associated type.

something like this maybe?

Yeah - that's much better.

-- update summary based on review -- rewrite explanation to be more clear and correct

MatthewPeterKelly · 2022-08-23T09:34:09Z

compiler/rustc_error_codes/src/error_codes/E0311.md

@@ -0,0 +1,70 @@
+This error occurs when there is insufficient information for the rust compiler
+to prove that a type has a long enough lifetime.


I think that type would be more correct as parameter.

MatthewPeterKelly · 2022-08-23T09:41:45Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+trait for a type `T`, so the `&mut self` reference has the lifetime of `T`.
+We know that `T` implements the `BorrowMut` trait returning a reference to `U`,
+and that `U` implements the `BorrowMut` trait returning a reference to `V`.


This isn't quite right either: T is a type and cannot have a lifetime. An object of type T, such as self can have a lifetime.

Really what we have is more like:

suppose that self has a lifetime of 'b

the output object of type V has a lifetime of 'c

If we split up the lines in the example we get:

let u_ref = self.borrow_mut(); // u_ref has lifetime `'b` matching `self` u_ref.borrow_mut() // u_ref has lifetime of `'c` matching the output

The compiler problem then boils to do failing to prove that 'c will be longer than 'b.

Perhaps the right approach here is to copy the failing example above and then add the lifetime annotations that the compiler attempts to add implicitly, similar to how they are shown in the examples in https://doc.rust-lang.org/book/ch10-03-lifetime-syntax.html.

I rewrote this to be more clear and correct.

MatthewPeterKelly · 2022-08-25T00:47:47Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+This error occurs when there is insufficient information for the rust compiler
+to prove that a type has a long enough lifetime.


Yeah - that's much better.

lcnr · 2022-09-05T05:21:33Z

@bors delegate+

bors · 2022-09-05T05:21:35Z

✌️ @MatthewPeterKelly can now approve this pull request

lcnr · 2022-09-05T05:26:30Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+compiler would have added an implied bound [implied
+bound](https://rust-lang.github.io/rfcs/2089-implied-bounds.html), causing this


Suggested change

compiler would have added an implied bound [implied

bound](https://rust-lang.github.io/rfcs/2089-implied-bounds.html), causing this

compiler would have added an

[implied bound](https://rust-lang.github.io/rfcs/2089-implied-bounds.html), causing this

oh wow, we really don't have a user facing doc for implied bounds xx that sucks

the rfc is about implied trait bounds. implied bounds already existed before that and are stable, unlike this rfc. We should really have a page in the reference for that

opened rust-lang/reference#1261 so maybe we should wait for that to land so that you can point there

Thanks for opening the PR to add the reference material. I added some comments on it and will hold this PR until that one lands.

lcnr · 2022-09-12T15:58:39Z

marking as blocked on rust-lang/reference#1261

Havvy · 2022-09-26T07:16:12Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+outlive `'anon` in `no_restriction()`.
+
+If `no_restriction()` were to use `&T` instead of `&()` as an argument, the
+compiler would have added an implied bound [implied


Suggested change

compiler would have added an implied bound [implied

compiler would have added an [implied

(Remove the double "implied bound")

Alternatively, remove the link for now, and then send a new PR when the reference PR lands. I don't think it's worth blocking on the reference PR.

I had figured that updating the docs would be quick, but it looks like it's going to be a more involved process. For now I removed the implied bounds link and will plan to merge this PR. Once rust-lang/reference#1261 has been merged I'll plan to open a smaller PR to add the reference link into the E0311.md docs.

…message-for-E0311

also update .stderr outputs

lcnr

2 nits, then r=me

lcnr · 2022-09-27T08:42:19Z

compiler/rustc_error_codes/src/error_codes/E0311.md

@@ -0,0 +1,42 @@
+This error occurs when there is an unsatisfied outlives bound involving an
+elided region on a generic type parameter or associated type.


Suggested change

elided region on a generic type parameter or associated type.

elided region and a generic type parameter or associated type.

lcnr · 2022-09-27T08:43:02Z

compiler/rustc_error_codes/src/error_codes/E0311.md

+lifetime `'anon` in `no_restriction()`. The only information available to the
+compiler is that `'anon` is valid for the duration of the function. When
+calling `with_restriction()`, the compiler requires the completely unrelated
+type parameter `T` to outlive `'anon` because of the `T: 'a bound` in


still relevant

lcnr · 2022-09-27T08:43:49Z

@bors delegate+

bors · 2022-09-27T08:43:52Z

✌️ @MatthewPeterKelly can now approve this pull request

MatthewPeterKelly · 2022-09-28T00:19:11Z

@bors r+ rollup

bors · 2022-09-28T00:19:13Z

📌 Commit c0d32fd has been approved by MatthewPeterKelly

It is now in the queue for this repository.

Rollup of 8 pull requests Successful merges: - rust-lang#100747 (Add long description and test for E0311) - rust-lang#102232 (Stabilize bench_black_box) - rust-lang#102288 (Suggest unwrapping `???<T>` if a method cannot be found on it but is present on `T`.) - rust-lang#102338 (Deny associated type bindings within associated type bindings) - rust-lang#102347 (Unescaping cleanups) - rust-lang#102348 (Tweak `FulfillProcessor`.) - rust-lang#102378 (Use already resolved `self_ty` in `confirm_fn_pointer_candidate`) - rust-lang#102380 (rustdoc: remove redundant mobile `.source > .sidebar` CSS) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

klensy · 2022-09-28T10:14:36Z

Merge commits kinda skipped review https://rustc-dev-guide.rust-lang.org/git.html#no-merge-policy

MatthewPeterKelly · 2022-09-29T00:57:15Z

Merge commits kinda skipped review https://rustc-dev-guide.rust-lang.org/git.html#no-merge-policy

You're totally right, and thanks for letting me know. This is my first PR for rust and I missed that policy when I was reading the docs. I'll be sure to do it correctly next time. Let me know if there is anything I should fix for this PR, but I suspect that we're locked-in at this point.

Rollup of 8 pull requests Successful merges: - rust-lang#100747 (Add long description and test for E0311) - rust-lang#102232 (Stabilize bench_black_box) - rust-lang#102288 (Suggest unwrapping `???<T>` if a method cannot be found on it but is present on `T`.) - rust-lang#102338 (Deny associated type bindings within associated type bindings) - rust-lang#102347 (Unescaping cleanups) - rust-lang#102348 (Tweak `FulfillProcessor`.) - rust-lang#102378 (Use already resolved `self_ty` in `confirm_fn_pointer_candidate`) - rust-lang#102380 (rustdoc: remove redundant mobile `.source > .sidebar` CSS) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

Add long description and test for E0311

fa91980

Adds a long description and unit test for the E0311 compiler error.

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Aug 19, 2022

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rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 19, 2022

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fix updated stderr outputs

08fa70e

GuillaumeGomez reviewed Aug 19, 2022

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Apply suggestions from code review

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Co-authored-by: Guillaume Gomez <[email protected]>

MatthewPeterKelly commented Aug 19, 2022

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fix line lengths

a9cefd0

fee1-dead reviewed Aug 23, 2022

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MatthewPeterKelly added 2 commits August 23, 2022 05:19

Improve E0311.md description

dbcc409

actually fix typo this time

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rust-highfive assigned lcnr and unassigned fee1-dead Aug 23, 2022

lcnr reviewed Aug 24, 2022

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Improve description again

dd7c48e

-- update summary based on review -- rewrite explanation to be more clear and correct

MatthewPeterKelly commented Aug 25, 2022

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fix wrapping

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MatthewPeterKelly requested a review from lcnr August 25, 2022 00:55

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lcnr added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 12, 2022

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MatthewPeterKelly added 2 commits September 26, 2022 19:59

Merge remote-tracking branch 'origin/master' into mpk/add-long-error-…

24aab52

…message-for-E0311

remove implied link bound per review

0d9c014

also update .stderr outputs

MatthewPeterKelly force-pushed the mpk/add-long-error-message-for-E0311 branch from df4dc2b to 0d9c014 Compare September 27, 2022 00:53

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review updates

c0d32fd

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-blocked Status: Blocked on something else such as an RFC or other implementation work. labels Sep 28, 2022

JohnTitor mentioned this pull request Sep 28, 2022

Rollup of 8 pull requests #102388

Merged

bors merged commit 49bc668 into rust-lang:master Sep 28, 2022

rustbot added this to the 1.66.0 milestone Sep 28, 2022

MatthewPeterKelly deleted the mpk/add-long-error-message-for-E0311 branch September 28, 2022 09:08

Ezrashaw mentioned this pull request Dec 22, 2022

docs/test: add UI test and long-form error docs for E0461 #106028

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GuillaumeGomez mentioned this pull request Dec 23, 2022

Add missing long error code explanations #61137

Closed

100 tasks

		E0311 occurs when there is insufficient information for the rust compiler to
		prove that some time has a long enough lifetime.

	to prove that the livetime of `U` is long enough to support the reference. To
	to prove that the lifetime of `U` is long enough to support the reference. To

		@@ -0,0 +1,49 @@
		This error occurs when there is insufficient information for the rust compiler
		to prove that some time has a long enough lifetime.

	to prove that some time has a long enough lifetime.
	to prove that a type has a long enough lifetime.

	This error occurs when there is insufficient information for the rust compiler
	to prove that a type has a long enough lifetime.
	This error occurs when there is an unsatisfied outlives bound on a generic type parameter or associated type.

		@@ -0,0 +1,70 @@
		This error occurs when there is insufficient information for the rust compiler
		to prove that a type has a long enough lifetime.

		compiler would have added an implied bound [implied
		bound](https://rust-lang.github.io/rfcs/2089-implied-bounds.html), causing this

	compiler would have added an implied bound [implied
	compiler would have added an [implied

		@@ -0,0 +1,42 @@
		This error occurs when there is an unsatisfied outlives bound involving an
		elided region on a generic type parameter or associated type.

	elided region on a generic type parameter or associated type.
	elided region and a generic type parameter or associated type.

Add long description and test for E0311 #100747

Add long description and test for E0311 #100747

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MatthewPeterKelly commented Aug 23, 2022

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lcnr commented Sep 5, 2022

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lcnr commented Sep 27, 2022

bors commented Sep 27, 2022

MatthewPeterKelly commented Sep 28, 2022

bors commented Sep 28, 2022

klensy commented Sep 28, 2022

MatthewPeterKelly commented Sep 29, 2022

fee1-dead commented Aug 23, 2022 •

edited

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