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

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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.

bors · 2025-09-16T08:46:04Z

☔ The latest upstream changes (presumably #146614) 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 · 2025-09-27T22:22:57Z

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 · 2025-09-28T19:35:36Z

@bors r=nnethercote

bors · 2025-09-28T19:35:39Z

📌 Commit cbe7ba6 has been approved by nnethercote

It is now in the queue for this repository.

bors · 2025-09-28T19:41:01Z

⌛ Testing commit cbe7ba6 with merge e587c0e...

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 · 2025-09-28T21:38:56Z

💔 Test failed - checks-actions

estebank · 2025-09-29T16:42:36Z

@bors r=nnethercote

bors · 2025-09-29T16:42:39Z

📌 Commit 3b3dc7b 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...

rust-log-analyzer · 2025-09-29T22:20:03Z

The job x86_64-mingw-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

---- [run-make] tests\run-make\lto-no-link-whole-rlib stdout ----

error: rmake recipe failed to complete
status: exit code: 1
command: "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\test\\run-make\\lto-no-link-whole-rlib\\rmake.exe"
stdout: none
--- stderr -------------------------------
command failed at line 15
Command { cmd: "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\stage2\\bin\\rustc.exe" "-L" "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\test\\run-make\\lto-no-link-whole-rlib\\rmake_out" "lib2.rs" "--target=x86_64-pc-windows-gnu", stdin_buf: None, stdin: None, stdout: None, stderr: None, drop_bomb: DropBomb { command: "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\stage2\\bin\\rustc.exe", defused: true, armed_location: Location { file: "D:\\a\\rust\\rust\\tests\\run-make\\lto-no-link-whole-rlib\\rmake.rs", line: 15, column: 5 } }, already_executed: true }
output status: `exit code: 0xc00000fd`
=== STDOUT ===



=== STDERR ===

thread 'main' (7496) has overflowed its stack
------------------------------------------

---- [run-make] tests\run-make\lto-no-link-whole-rlib stdout end ----

failures:
    [run-make] tests\run-make\lto-no-link-whole-rlib

test result: FAILED. 299 passed; 1 failed; 141 ignored; 0 measured; 5 filtered out; finished in 223.46s

Some tests failed in compiletest suite=run-make mode=run-make host=x86_64-pc-windows-gnu target=x86_64-pc-windows-gnu
Bootstrap failed while executing `test --stage 2 --skip=compiler --skip=src`
Build completed unsuccessfully in 2:29:27
make: *** [Makefile:123: ci-mingw-x] Error 1
  local time: Mon Sep 29 22:19:45 CUT 2025
  network time: Mon, 29 Sep 2025 22:19:46 GMT
##[error]Process completed with exit code 2.
Post job cleanup.
[command]"C:\Program Files\Git\bin\git.exe" version

bors · 2025-09-29T22:20:25Z

💔 Test failed - checks-actions

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