When a trait isn't implemented, but another similar impl is found, point at it #145640

estebank · 2025-08-20T01:32:44Z

error[E0277]: the trait bound `u32: Trait` is not satisfied
  --> $DIR/trait_objects_fail.rs:26:9
   |
LL |     foo(&10_u32);
   |         ^^^^^^^ the trait `Trait` is not implemented for `u32`
   |
help: the trait `Trait<12>` is not implemented for `u32`
      but trait `Trait<2>` is implemented for it
  --> $DIR/trait_objects_fail.rs:7:1
   |
LL | impl Trait<2> for u32 {}
   | ^^^^^^^^^^^^^^^^^^^^^
   = note: required for the cast from `&u32` to `&dyn Trait`

Pointing at the impl definition that could apply given a different self type is particularly useful when it has a blanket self type, as it might not be obvious and is not trivially greppable:

error[E0277]: the trait bound `RawImpl<_>: Raw<_>` is not satisfied
  --> $DIR/issue-62742.rs:4:5
   |
LL |     WrongImpl::foo(0i32);
   |     ^^^^^^^^^ unsatisfied trait bound
   |
help: the trait `Raw<_>` is not implemented for `RawImpl<_>`
      but trait `Raw<[_]>` is implemented for it
  --> $DIR/issue-62742.rs:29:1
   |
LL | impl<T> Raw<[T]> for RawImpl<T> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `SafeImpl`
  --> $DIR/issue-62742.rs:33:35
   |
LL | pub struct SafeImpl<T: ?Sized, A: Raw<T>>(PhantomData<(A, T)>);
   |                                   ^^^^^^ required by this bound in `SafeImpl`

rustbot · 2025-08-20T01:32:48Z

r? @nnethercote

rustbot has assigned @nnethercote.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

rustbot · 2025-08-20T01:32:50Z

rustc_errors::emitter was changed

cc @Muscraft

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

nnethercote · 2025-08-22T05:16:46Z

Looks fine, r=me once everything is green.

estebank · 2025-08-23T17:57:25Z

@bors r=nnethercote

bors · 2025-08-23T17:57:28Z

📌 Commit 3f07cda has been approved by nnethercote

It is now in the queue for this repository.

jhpratt · 2025-08-23T23:35:24Z

@bors r- (has merge conflicts)

bors · 2025-08-24T00:46:45Z

☔ The latest upstream changes (presumably #145706) made this pull request unmergeable. Please resolve the merge conflicts.

estebank · 2025-08-24T21:06:05Z

@bors r=nnethercote rollup=never

bors · 2025-08-24T21:06:08Z

📌 Commit 898ddc3 has been approved by nnethercote

It is now in the queue for this repository.

When a trait isn't implemented, but another similar impl is found, point at it ``` error[E0277]: the trait bound `u32: Trait` is not satisfied --> $DIR/trait_objects_fail.rs:26:9 | LL | foo(&10_u32); | ^^^^^^^ the trait `Trait` is not implemented for `u32` | help: the trait `Trait<12>` is not implemented for `u32` but trait `Trait<2>` is implemented for it --> $DIR/trait_objects_fail.rs:7:1 | LL | impl Trait<2> for u32 {} | ^^^^^^^^^^^^^^^^^^^^^ = note: required for the cast from `&u32` to `&dyn Trait` ``` Pointing at the `impl` definition that *could* apply given a different self type is *particularly* useful when it has a blanket self type, as it might not be obvious and is not trivially greppable: ``` error[E0277]: the trait bound `RawImpl<_>: Raw<_>` is not satisfied --> $DIR/issue-62742.rs:4:5 | LL | WrongImpl::foo(0i32); | ^^^^^^^^^ unsatisfied trait bound | help: the trait `Raw<_>` is not implemented for `RawImpl<_>` but trait `Raw<[_]>` is implemented for it --> $DIR/issue-62742.rs:29:1 | LL | impl<T> Raw<[T]> for RawImpl<T> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ note: required by a bound in `SafeImpl` --> $DIR/issue-62742.rs:33:35 | LL | pub struct SafeImpl<T: ?Sized, A: Raw<T>>(PhantomData<(A, T)>); | ^^^^^^ required by this bound in `SafeImpl` ```

bors · 2025-09-29T19:41:48Z

⌛ Testing commit 3b3dc7b with merge 793789c...

bors · 2025-09-29T22:20:25Z

💔 Test failed - checks-actions

bors · 2025-10-12T13:59:16Z

☔ The latest upstream changes (presumably #147603) made this pull request unmergeable. Please resolve the merge conflicts.

…int at it: ``` error[E0277]: the trait bound `u32: Trait` is not satisfied --> $DIR/trait_objects_fail.rs:26:9 | LL | foo(&10_u32); | ^^^^^^^ the trait `Trait` is not implemented for `u32` | help: the trait `Trait<12>` is not implemented for `u32` but trait `Trait<2>` is implemented for it --> $DIR/trait_objects_fail.rs:7:1 | LL | impl Trait<2> for u32 {} | ^^^^^^^^^^^^^^^^^^^^^ = note: required for the cast from `&u32` to `&dyn Trait` ``` Pointing at the `impl` definition that *could* apply given a different self type is particularly useful when it has a blanket self type, as it might not be obvious and is not trivially greppable: ``` error[E0277]: the trait bound `RawImpl<_>: Raw<_>` is not satisfied --> $DIR/issue-62742.rs:4:5 | LL | WrongImpl::foo(0i32); | ^^^^^^^^^ unsatisfied trait bound | help: the trait `Raw<_>` is not implemented for `RawImpl<_>` but trait `Raw<[_]>` is implemented for it --> $DIR/issue-62742.rs:29:1 | LL | impl<T> Raw<[T]> for RawImpl<T> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ note: required by a bound in `SafeImpl` --> $DIR/issue-62742.rs:33:35 | LL | pub struct SafeImpl<T: ?Sized, A: Raw<T>>(PhantomData<(A, T)>); | ^^^^^^ required by this bound in `SafeImpl` ```

…them ``` error[E0277]: the trait bound `[[u16; 3]; 2]: Bar` is not satisfied --> $DIR/issue-67185-2.rs:21:6 | LL | impl Foo for FooImpl {} | ^^^ the trait `Bar` is not implemented for `[[u16; 3]; 2]` | help: the following other types implement trait `Bar` --> $DIR/issue-67185-2.rs:9:1 | LL | impl Bar for [u16; 4] {} | ^^^^^^^^^^^^^^^^^^^^^ `[u16; 4]` LL | impl Bar for [[u16; 3]; 3] {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^ `[[u16; 3]; 3]` note: required by a bound in `Foo` --> $DIR/issue-67185-2.rs:14:30 | LL | trait Foo | --- required by a bound in this trait LL | where LL | [<u8 as Baz>::Quaks; 2]: Bar, | ^^^ required by this bound in `Foo` ```

rustbot · 2025-10-31T20:44:11Z

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 · 2025-10-31T23:53:15Z

@bors r=nnethercote

bors · 2025-10-31T23:53:18Z

📌 Commit 32aa599 has been approved by nnethercote

It is now in the queue for this repository.

bors · 2025-11-01T20:11:29Z

⌛ Testing commit 32aa599 with merge bd3ac03...

bors · 2025-11-01T23:47:31Z

☀️ Test successful - checks-actions
Approved by: nnethercote
Pushing bd3ac03 to master...

github-actions · 2025-11-01T23:50:19Z

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 fca2e94 (parent) -> bd3ac03 (this PR)

Test differences

Show 10 test diffs

Stage 1

[ui] tests/ui/allocator/not-an-allocator.rs: pass -> [missing] (J0)
[ui] tests/ui/allocator/not-an-allocator.rs#u: [missing] -> pass (J0)
[ui] tests/ui/allocator/not-an-allocator.rs#w: [missing] -> ignore (only executed when the operating system is windows) (J0)

Stage 2

[ui] tests/ui/allocator/not-an-allocator.rs#u: [missing] -> ignore (only executed when the target family is unix) (J1)
[ui] tests/ui/allocator/not-an-allocator.rs#w: [missing] -> pass (J1)
[ui] tests/ui/allocator/not-an-allocator.rs: pass -> [missing] (J2)
[ui] tests/ui/allocator/not-an-allocator.rs#u: [missing] -> pass (J3)
[ui] tests/ui/allocator/not-an-allocator.rs#w: [missing] -> ignore (only executed when the operating system is windows) (J3)

Additionally, 2 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard bd3ac0330018c23b111bbee176f32c377be7b319 --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

x86_64-gnu-gcc: 3060.1s -> 4101.8s (+34.0%)
x86_64-gnu-llvm-20: 2455.4s -> 2892.2s (+17.8%)
x86_64-gnu-debug: 6696.7s -> 7798.0s (+16.4%)
x86_64-gnu-stable: 6528.5s -> 7560.2s (+15.8%)
i686-gnu-2: 5487.9s -> 6284.5s (+14.5%)
dist-aarch64-windows-gnullvm: 4489.0s -> 5111.7s (+13.9%)
x86_64-rust-for-linux: 2622.9s -> 2984.9s (+13.8%)
dist-android: 1606.1s -> 1388.0s (-13.6%)
test-various: 6050.3s -> 6844.7s (+13.1%)
i686-gnu-nopt-1: 7274.2s -> 8132.7s (+11.8%)

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 · 2025-11-02T00:58:58Z

Finished benchmarking commit (bd3ac03): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary 1.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.6%	[0.8%, 2.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.6%	[0.8%, 2.4%]	2

Cycles

Results (secondary -0.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.8%	[2.8%, 2.8%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.2%	[-2.3%, -2.0%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 474.465s -> 474.434s (-0.01%)
Artifact size: 390.82 MiB -> 390.87 MiB (0.01%)

rustbot assigned nnethercote Aug 20, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 20, 2025

This comment has been minimized.

Sign in to view

estebank force-pushed the point-at-impl-e0277 branch from 3967b4e to c6c62f4 Compare August 20, 2025 17:59

rustbot added the WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) label Aug 20, 2025

This comment has been minimized.

Sign in to view

nnethercote added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 22, 2025

estebank force-pushed the point-at-impl-e0277 branch from c6c62f4 to a05bf52 Compare August 22, 2025 18:59

This comment has been minimized.

Sign in to view

This comment was marked as resolved.

Sign in to view

estebank force-pushed the point-at-impl-e0277 branch from a05bf52 to 3f07cda Compare August 23, 2025 16:12

This comment has been minimized.

Sign in to view

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 Aug 23, 2025

jhpratt mentioned this pull request Aug 23, 2025

Rollup of 6 pull requests #145802

Closed

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Aug 23, 2025

estebank force-pushed the point-at-impl-e0277 branch from 3f07cda to 898ddc3 Compare August 24, 2025 16:55

This comment has been minimized.

Sign in to view

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Sep 29, 2025

This comment has been minimized.

Sign in to view

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Sep 29, 2025

nnethercote added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 13, 2025

estebank added 4 commits October 31, 2025 20:38

Fix dlltool-failed test

ef8ed4c

Account for #[rustc_reservation_impl] when pointing at potential impls

c9c7272

estebank force-pushed the point-at-impl-e0277 branch from 3b3dc7b to c9c7272 Compare October 31, 2025 20:44

This comment has been minimized.

Sign in to view

Ignore file length lint for now

32aa599

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 Oct 31, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Nov 1, 2025

bors merged commit bd3ac03 into rust-lang:master Nov 1, 2025
12 checks passed

rustbot added this to the 1.93.0 milestone Nov 1, 2025

bors mentioned this pull request Nov 2, 2025

Add a diagnostic for similarly named traits #144674

Open

When a trait isn't implemented, but another similar impl is found, point at it #145640

When a trait isn't implemented, but another similar impl is found, point at it #145640

Uh oh!

Conversation

estebank commented Aug 20, 2025

Uh oh!

rustbot commented Aug 20, 2025

Uh oh!

rustbot commented Aug 20, 2025

Uh oh!

This comment has been minimized.

This comment has been minimized.

nnethercote commented Aug 22, 2025

Uh oh!

This comment has been minimized.

This comment was marked as resolved.

This comment has been minimized.

estebank commented Aug 23, 2025

Uh oh!

bors commented Aug 23, 2025

Uh oh!

jhpratt commented Aug 23, 2025

Uh oh!

bors commented Aug 24, 2025

Uh oh!

This comment has been minimized.

estebank commented Aug 24, 2025

Uh oh!

bors commented Aug 24, 2025

Uh oh!

bors commented Sep 29, 2025

Uh oh!

This comment has been minimized.

bors commented Sep 29, 2025

Uh oh!

bors commented Oct 12, 2025

Uh oh!

rustbot commented Oct 31, 2025

Uh oh!

This comment has been minimized.

estebank commented Oct 31, 2025

Uh oh!

bors commented Oct 31, 2025

Uh oh!

bors commented Nov 1, 2025

Uh oh!

bors commented Nov 1, 2025

Uh oh!

Uh oh!

github-actions bot commented Nov 1, 2025

Test differences

Stage 1

Stage 2

Job duration changes

Uh oh!

rust-timer commented Nov 2, 2025

Overall result: no relevant changes - no action needed

Instruction count

Max RSS (memory usage)

Cycles

Binary size

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

7 participants