Tweak output of missing lifetime on associated type #145314

estebank · 2025-08-12T17:33:41Z

Follow up to #135602.

Previously we only showed the trait's assoc item if the trait was local, because we were looking for a small span only for the generics, which we don't have for foreign traits. We now use def_span for the item, so we at least provide some context, even if its span is too wide.

error[E0195]: lifetime parameters or bounds on type `IntoIter` do not match the trait declaration
   --> tests/ui/lifetimes/missing-lifetime-in-assoc-type-4.rs:7:18
    |
7   |     type IntoIter<'a> = std::collections::btree_map::Values<'a, i32, T>;
    |                  ^^^^ lifetimes do not match type in trait
    |
   ::: /home/gh-estebank/rust/library/core/src/iter/traits/collect.rs:292:5
    |
292 |     type IntoIter: Iterator<Item = Self::Item>;
    |     ------------------------------------------ lifetimes in impl do not match this type in trait

Given an associated item that needs a named lifetime, look at the enclosing impl item for one. If there is none, look at the self type and the implemented trait to see if either of those has an anonimous lifetime. If so, suggest adding a named lifetime.

error: in the trait associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type
  --> $DIR/missing-lifetime-in-assoc-type-2.rs:5:17
   |
LL |     type Item = &T;
   |                 ^ this lifetime must come from the implemented type
   |
help: add a lifetime to the impl block and use it in the self type and associated type
   |
LL ~ impl<'a> IntoIterator for &'a S {
LL ~     type Item = &'a T;
   |

Move the previous long message to a note and use a shorter primary message:

error: missing lifetime in associated type
  --> $DIR/missing-lifetime-in-assoc-type-1.rs:9:17
   |
LL | impl<'a> IntoIterator for &S {
   |     ---- there is a named lifetime specified on the impl block you could use
...
LL |     type Item = &T;
   |                 ^ this lifetime must come from the implemented type
   |
note: in the trait the associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type
  --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
help: consider using the lifetime from the impl block
   |
LL |     type Item = &'a T;
   |                  ++

r? @Nadrieril

rustbot · 2025-08-12T17:33:46Z

Nadrieril is currently at their maximum review capacity.
They may take a while to respond.

Nadrieril · 2025-10-08T08:43:14Z

Waiting for #135602 then a rebase.

@rustbot author

rustbot · 2025-10-08T08:43:18Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

bors · 2025-11-01T21:04:54Z

☔ The latest upstream changes (presumably #148356) made this pull request unmergeable. Please resolve the merge conflicts.

Previously we only showed the trait's assoc item if the trait was local, because we were looking for a small span only for the generics, which we don't have for foreign traits. We now use `def_span` for the item, so we at least provide some context, even if its span is too wide. ``` error[E0195]: lifetime parameters or bounds on type `IntoIter` do not match the trait declaration --> tests/ui/lifetimes/missing-lifetime-in-assoc-type-4.rs:7:18 | 7 | type IntoIter<'a> = std::collections::btree_map::Values<'a, i32, T>; | ^^^^ lifetimes do not match type in trait | ::: /home/gh-estebank/rust/library/core/src/iter/traits/collect.rs:292:5 | 292 | type IntoIter: Iterator<Item = Self::Item>; | ------------------------------------------ lifetimes in impl do not match this type in trait ```

Given an associated item that needs a named lifetime, look at the enclosing `impl` item for one. If there is none, look at the self type and the implemented trait to see if either of those has an anonimous lifetime. If so, suggest adding a named lifetime. ``` error: in the trait associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type --> $DIR/missing-lifetime-in-assoc-type-2.rs:5:17 | LL | type Item = &T; | ^ this lifetime must come from the implemented type | help: add a lifetime to the impl block and use it in the self type and associated type | LL ~ impl<'a> IntoIterator for &'a S { LL ~ type Item = &'a T; | ```

Move the previous long message to a note and use a shorter primary message: ``` error: missing lifetime in associated type --> $DIR/missing-lifetime-in-assoc-type-1.rs:9:17 | LL | impl<'a> IntoIterator for &S { | ---- there is a named lifetime specified on the impl block you could use ... LL | type Item = &T; | ^ this lifetime must come from the implemented type | note: in the trait the associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL help: consider using the lifetime from the impl block | LL | type Item = &'a T; | ++ ```

rustbot · 2025-11-03T02:23:21Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

estebank · 2025-11-03T02:23:28Z

@rustbot ready

Nadrieril · 2025-11-04T15:08:41Z

That's a much better error, ty

@bors r+

bors · 2025-11-04T15:08:47Z

📌 Commit 817cf4b has been approved by Nadrieril

It is now in the queue for this repository.

bors · 2025-11-04T15:08:48Z

🌲 The tree is currently closed for pull requests below priority 100. This pull request will be tested once the tree is reopened.

…eril Tweak output of missing lifetime on associated type Follow up to rust-lang#135602. Previously we only showed the trait's assoc item if the trait was local, because we were looking for a small span only for the generics, which we don't have for foreign traits. We now use `def_span` for the item, so we at least provide some context, even if its span is too wide. ``` error[E0195]: lifetime parameters or bounds on type `IntoIter` do not match the trait declaration --> tests/ui/lifetimes/missing-lifetime-in-assoc-type-4.rs:7:18 | 7 | type IntoIter<'a> = std::collections::btree_map::Values<'a, i32, T>; | ^^^^ lifetimes do not match type in trait | ::: /home/gh-estebank/rust/library/core/src/iter/traits/collect.rs:292:5 | 292 | type IntoIter: Iterator<Item = Self::Item>; | ------------------------------------------ lifetimes in impl do not match this type in trait ``` Given an associated item that needs a named lifetime, look at the enclosing `impl` item for one. If there is none, look at the self type and the implemented trait to see if either of those has an anonimous lifetime. If so, suggest adding a named lifetime. ``` error: in the trait associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type --> $DIR/missing-lifetime-in-assoc-type-2.rs:5:17 | LL | type Item = &T; | ^ this lifetime must come from the implemented type | help: add a lifetime to the impl block and use it in the self type and associated type | LL ~ impl<'a> IntoIterator for &'a S { LL ~ type Item = &'a T; | ``` Move the previous long message to a note and use a shorter primary message: ``` error: missing lifetime in associated type --> $DIR/missing-lifetime-in-assoc-type-1.rs:9:17 | LL | impl<'a> IntoIterator for &S { | ---- there is a named lifetime specified on the impl block you could use ... LL | type Item = &T; | ^ this lifetime must come from the implemented type | note: in the trait the associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL help: consider using the lifetime from the impl block | LL | type Item = &'a T; | ++ ``` r? ``@Nadrieril``

…eril Tweak output of missing lifetime on associated type Follow up to rust-lang#135602. Previously we only showed the trait's assoc item if the trait was local, because we were looking for a small span only for the generics, which we don't have for foreign traits. We now use `def_span` for the item, so we at least provide some context, even if its span is too wide. ``` error[E0195]: lifetime parameters or bounds on type `IntoIter` do not match the trait declaration --> tests/ui/lifetimes/missing-lifetime-in-assoc-type-4.rs:7:18 | 7 | type IntoIter<'a> = std::collections::btree_map::Values<'a, i32, T>; | ^^^^ lifetimes do not match type in trait | ::: /home/gh-estebank/rust/library/core/src/iter/traits/collect.rs:292:5 | 292 | type IntoIter: Iterator<Item = Self::Item>; | ------------------------------------------ lifetimes in impl do not match this type in trait ``` Given an associated item that needs a named lifetime, look at the enclosing `impl` item for one. If there is none, look at the self type and the implemented trait to see if either of those has an anonimous lifetime. If so, suggest adding a named lifetime. ``` error: in the trait associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type --> $DIR/missing-lifetime-in-assoc-type-2.rs:5:17 | LL | type Item = &T; | ^ this lifetime must come from the implemented type | help: add a lifetime to the impl block and use it in the self type and associated type | LL ~ impl<'a> IntoIterator for &'a S { LL ~ type Item = &'a T; | ``` Move the previous long message to a note and use a shorter primary message: ``` error: missing lifetime in associated type --> $DIR/missing-lifetime-in-assoc-type-1.rs:9:17 | LL | impl<'a> IntoIterator for &S { | ---- there is a named lifetime specified on the impl block you could use ... LL | type Item = &T; | ^ this lifetime must come from the implemented type | note: in the trait the associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL help: consider using the lifetime from the impl block | LL | type Item = &'a T; | ++ ``` r? ```@Nadrieril```

…eril Tweak output of missing lifetime on associated type Follow up to rust-lang#135602. Previously we only showed the trait's assoc item if the trait was local, because we were looking for a small span only for the generics, which we don't have for foreign traits. We now use `def_span` for the item, so we at least provide some context, even if its span is too wide. ``` error[E0195]: lifetime parameters or bounds on type `IntoIter` do not match the trait declaration --> tests/ui/lifetimes/missing-lifetime-in-assoc-type-4.rs:7:18 | 7 | type IntoIter<'a> = std::collections::btree_map::Values<'a, i32, T>; | ^^^^ lifetimes do not match type in trait | ::: /home/gh-estebank/rust/library/core/src/iter/traits/collect.rs:292:5 | 292 | type IntoIter: Iterator<Item = Self::Item>; | ------------------------------------------ lifetimes in impl do not match this type in trait ``` Given an associated item that needs a named lifetime, look at the enclosing `impl` item for one. If there is none, look at the self type and the implemented trait to see if either of those has an anonimous lifetime. If so, suggest adding a named lifetime. ``` error: in the trait associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type --> $DIR/missing-lifetime-in-assoc-type-2.rs:5:17 | LL | type Item = &T; | ^ this lifetime must come from the implemented type | help: add a lifetime to the impl block and use it in the self type and associated type | LL ~ impl<'a> IntoIterator for &'a S { LL ~ type Item = &'a T; | ``` Move the previous long message to a note and use a shorter primary message: ``` error: missing lifetime in associated type --> $DIR/missing-lifetime-in-assoc-type-1.rs:9:17 | LL | impl<'a> IntoIterator for &S { | ---- there is a named lifetime specified on the impl block you could use ... LL | type Item = &T; | ^ this lifetime must come from the implemented type | note: in the trait the associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL help: consider using the lifetime from the impl block | LL | type Item = &'a T; | ++ ``` r? ````@Nadrieril````

Rollup of 5 pull requests Successful merges: - #145314 (Tweak output of missing lifetime on associated type) - #147803 (Add -Zannotate-moves for profiler visibility of move/copy operations (codegen)) - #147925 (Fix tests for big-endian) - #148341 (compiler: Fix a couple issues around cargo feature unification) - #148371 (Dogfood `trim_{suffix|prefix}` in compiler) r? `@ghost` `@rustbot` modify labels: rollup

bors · 2025-11-04T21:37:47Z

⌛ Testing commit 817cf4b with merge 6e41e61...

bors · 2025-11-05T00:42:16Z

☀️ Test successful - checks-actions
Approved by: Nadrieril
Pushing 6e41e61 to master...

github-actions · 2025-11-05T00:46:01Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing f15a7f3 (parent) -> 6e41e61 (this PR)

Test differences

Show 24 test diffs

Stage 1

[ui] tests/ui/lifetimes/missing-lifetime-in-assoc-type-6.rs: [missing] -> pass (J1)

Stage 2

[ui] tests/ui/lifetimes/missing-lifetime-in-assoc-type-6.rs: [missing] -> pass (J0)

Additionally, 22 doctest diffs were found. These are ignored, as they are noisy.

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Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 6e41e6197735bcb06c71c6d7a46de13119138578 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-aarch64-apple: 8415.7s -> 6938.1s (-17.6%)
x86_64-msvc-2: 6477.4s -> 7256.4s (+12.0%)
dist-x86_64-solaris: 5612.4s -> 5135.1s (-8.5%)
i686-gnu-nopt-2: 7317.1s -> 7936.2s (+8.5%)
dist-powerpc-linux: 5177.5s -> 4739.4s (-8.5%)
aarch64-gnu-debug: 3846.2s -> 4148.8s (+7.9%)
pr-check-1: 1472.8s -> 1588.1s (+7.8%)
dist-aarch64-msvc: 6058.1s -> 5619.8s (-7.2%)
dist-x86_64-musl: 7594.9s -> 7059.0s (-7.1%)
x86_64-gnu-gcc: 3051.8s -> 3256.4s (+6.7%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-11-05T07:59:21Z

Finished benchmarking commit (6e41e61): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.5%	[-0.6%, -0.5%]	3
All ❌✅ (primary)	-	-	0

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	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-0.7%, -0.7%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.7%	[-0.7%, -0.7%]	1

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Results (secondary -2.2%)

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	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 474.825s -> 475.404s (0.12%)
Artifact size: 390.60 MiB -> 390.71 MiB (0.03%)

rustbot assigned Nadrieril Aug 12, 2025

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Tweak output of missing lifetime on associated type #135602

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Nadrieril added the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Oct 8, 2025

estebank added 6 commits November 3, 2025 02:13

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0a27256

fix tidy

4e09cd1

fix tests

817cf4b

estebank force-pushed the issue-135589-all branch from 648093d to 817cf4b Compare November 3, 2025 02:23

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 Nov 4, 2025

matthiaskrgr mentioned this pull request Nov 4, 2025

Rollup of 4 pull requests #148485

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Rollup of 3 pull requests #148489

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Rollup of 5 pull requests #148496

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bors added the merged-by-bors This PR was explicitly merged by bors. label Nov 5, 2025

bors merged commit 6e41e61 into rust-lang:master Nov 5, 2025
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rustbot added this to the 1.93.0 milestone Nov 5, 2025

Tweak output of missing lifetime on associated type #145314

Tweak output of missing lifetime on associated type #145314

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