Tweak the rendering of "not general enough" errors on the old trait solver by estebank · Pull Request #163613 · rust-lang/rust

estebank · 2026-10-01T16:14:08Z

Use a note to point at the source of the unmet obligation instead of labels (makes the order of the error consistent regardless of the order of the code)
Point at the found impl that doesn't meet the obligation
In a few cases, remove the same information being printed twice
Support #[primary_span] span: Option<Span> in Subdiagnostics

error: implementation of `TheTrait` is not general enough
  --> $DIR/associated-types-eq-hr.rs:96:5
   |
LL |     tuple_one::<Tuple>();
   |     ^^^^^^^^^^^^^^^^^^^^
   |
note: `Tuple` must implement `TheTrait<(&'0 isize, &'1 isize)>`, for any two lifetimes `'0` and `'1`...
  --> $DIR/associated-types-eq-hr.rs:59:8
   |
LL | fn tuple_one<T>()
LL | where
LL |     T: for<'x, 'y> TheTrait<(&'x isize, &'y isize), A = &'x isize>,
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `tuple_one`
note: ...but it actually implements `TheTrait<(&'2 isize, &'2 isize)>`, for some specific lifetime `'2`
  --> $DIR/associated-types-eq-hr.rs:35:1
   |
LL | impl<'a> TheTrait<(&'a isize, &'a isize)> for Tuple {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The output now is closer to what the next trait solver will emit (E0277).

rustbot · 2026-10-01T16:14:11Z

rustc_macros::diagnostics was changed

cc @TaKO8Ki, @JonathanBrouwer

rustc_error_messages was changed

cc @TaKO8Ki

rustbot · 2026-10-01T16:14:14Z

r? @JonathanBrouwer

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JonathanBrouwer

r=me after solving conflicts and nits

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JonathanBrouwer · 2026-10-03T08:55:38Z

@rustbot author

rustbot · 2026-10-03T08:55:42Z

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

``` error: implementation of `TheTrait` is not general enough --> $DIR/associated-types-eq-hr.rs:96:5 | LL | fn tuple_one<T>() | --------- due to a where-clause on `tuple_one`... LL | where LL | T: for<'x, 'y> TheTrait<(&'x isize, &'y isize), A = &'x isize>, | ----------------------------------------------------------- unsatisfied where-clause on `tuple_one` ... LL | tuple_one::<Tuple>(); | ^^^^^^^^^^^^^^^^^^^^ | = note: ...`Tuple` must implement `TheTrait<(&'0 isize, &'1 isize)>`, for any two lifetimes `'0` and `'1`... note: ...but it actually implements `TheTrait<(&'2 isize, &'2 isize)>`, for some specific lifetime `'2` --> $DIR/associated-types-eq-hr.rs:35:1 | LL | impl<'a> TheTrait<(&'a isize, &'a isize)> for Tuple { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ```

Use a span note instead of span labels so that when talking about the trait that should have been implemented, we always point at where the obligation was introduced in a consistent place. ``` error: implementation of `TheTrait` is not general enough --> $DIR/associated-types-eq-hr.rs:96:5 | LL | tuple_one::<Tuple>(); | ^^^^^^^^^^^^^^^^^^^^ | note: `Tuple` must implement `TheTrait<(&'0 isize, &'1 isize)>`, for any two lifetimes `'0` and `'1`... --> $DIR/associated-types-eq-hr.rs:59:8 | LL | fn tuple_one<T>() | --------- due to a where-clause on `tuple_one` LL | where LL | T: for<'x, 'y> TheTrait<(&'x isize, &'y isize), A = &'x isize>, | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied where-clause on `tuple_one` note: ...but it actually implements `TheTrait<(&'2 isize, &'2 isize)>`, for some specific lifetime `'2` --> $DIR/associated-types-eq-hr.rs:35:1 | LL | impl<'a> TheTrait<(&'a isize, &'a isize)> for Tuple { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ```

``` error: implementation of `Lengthen` is not general enough --> $DIR/gat-bounds-not-checked-with-right-substitutions.rs:20:20 | LL | type Gat<'a> = &'a str; | ^^^^^^^ | note: `Lengthen<&'0 str>` would have to be implemented for the type `&'a str`, for any lifetime `'0`... --> $DIR/gat-bounds-not-checked-with-right-substitutions.rs:12:19 | LL | trait Gat { LL | type Gat<'a>: for<'b> Lengthen<Self::Gat<'b>>; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Gat::Gat` = note: ...but `Lengthen<&'1 str>` is actually implemented for the type `&'1 str`, for some specific lifetime `'1` ```

rustbot · 2026-10-03T17:28:10Z

This PR was rebased onto a different main 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 · 2026-10-03T19:16:58Z

@bors r=JonathanBrouwer

rust-bors · 2026-10-03T19:17:01Z

📌 Commit 337f98d has been approved by JonathanBrouwer

It is now in the queue for this repository.

…athanBrouwer Tweak the rendering of "not general enough" errors on the old trait solver - Use a note to point at the source of the unmet obligation instead of labels (makes the order of the error consistent regardless of the order of the code) - Point at the found impl that doesn't meet the obligation - In a few cases, remove the same information being printed twice - Support `#[primary_span] span: Option<Span>` in `Subdiagnostic`s ``` error: implementation of `TheTrait` is not general enough --> $DIR/associated-types-eq-hr.rs:96:5 | LL | tuple_one::<Tuple>(); | ^^^^^^^^^^^^^^^^^^^^ | note: `Tuple` must implement `TheTrait<(&'0 isize, &'1 isize)>`, for any two lifetimes `'0` and `'1`... --> $DIR/associated-types-eq-hr.rs:59:8 | LL | fn tuple_one<T>() LL | where LL | T: for<'x, 'y> TheTrait<(&'x isize, &'y isize), A = &'x isize>, | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `tuple_one` note: ...but it actually implements `TheTrait<(&'2 isize, &'2 isize)>`, for some specific lifetime `'2` --> $DIR/associated-types-eq-hr.rs:35:1 | LL | impl<'a> TheTrait<(&'a isize, &'a isize)> for Tuple { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``` The output now is closer to what the next trait solver will emit (E0277).

Rollup of 18 pull requests Successful merges: - #158102 (When compiling without a specified `--edition`, emit a message) - #162027 (std: add `fs::rename_noreplace`) - #162761 (Lower attributes for functions without bodies) - #163161 (implement FCW for `rustc_allowed_through_unstable_modules` items) - #163613 (Tweak the rendering of "not general enough" errors on the old trait solver) - #162062 (core: fix the docs of PanicInfo::location) - #163140 (document safety requirements for atomic intrinsics) - #163342 (Don't imply incorrect things about `Global` in the docs of `System`) - #163445 (Add safety comments for alloc::str) - #163503 (Mark Rc strong/weak count methods must_use) - #163548 (fs::set_permissions_nofollow: Android support, test cleanup) - #163585 ([triagebot] Create `debugger_visualizer` assign group) - #163597 (Add `SplitPathsRef` implementation for motor to make std build) - #163602 (Move media & home dirs tests to fs tests.) - #163667 (Finalize changes on expect messages for library/core/src/fmt/mod.rs) - #163682 ([rustdoc] Correctly link to (imported) enum variants with "jump to def") - #163683 (Fix GCC codegen backend comment in bootstrap) - #163703 (Move more `rustdoc-html tests` in the right location) Failed merges: - #161491 (Rip out old solver coherence)

Rollup of 18 pull requests Successful merges: - #158102 (When compiling without a specified `--edition`, emit a message) - #162761 (Lower attributes for functions without bodies) - #163161 (implement FCW for `rustc_allowed_through_unstable_modules` items) - #163613 (Tweak the rendering of "not general enough" errors on the old trait solver) - #162062 (core: fix the docs of PanicInfo::location) - #163140 (document safety requirements for atomic intrinsics) - #163342 (Don't imply incorrect things about `Global` in the docs of `System`) - #163445 (Add safety comments for alloc::str) - #163503 (Mark Rc strong/weak count methods must_use) - #163548 (fs::set_permissions_nofollow: Android support, test cleanup) - #163585 ([triagebot] Create `debugger_visualizer` assign group) - #163597 (Add `SplitPathsRef` implementation for motor to make std build) - #163602 (Move media & home dirs tests to fs tests.) - #163667 (Finalize changes on expect messages for library/core/src/fmt/mod.rs) - #163682 ([rustdoc] Correctly link to (imported) enum variants with "jump to def") - #163683 (Fix GCC codegen backend comment in bootstrap) - #163703 (Move more `rustdoc-html tests` in the right location) - #163725 (some crashes fixed with next-solver) Failed merges: - #161491 (Rip out old solver coherence)

Rollup merge of #163613 - estebank:not-general-enough, r=JonathanBrouwer Tweak the rendering of "not general enough" errors on the old trait solver - Use a note to point at the source of the unmet obligation instead of labels (makes the order of the error consistent regardless of the order of the code) - Point at the found impl that doesn't meet the obligation - In a few cases, remove the same information being printed twice - Support `#[primary_span] span: Option<Span>` in `Subdiagnostic`s ``` error: implementation of `TheTrait` is not general enough --> $DIR/associated-types-eq-hr.rs:96:5 | LL | tuple_one::<Tuple>(); | ^^^^^^^^^^^^^^^^^^^^ | note: `Tuple` must implement `TheTrait<(&'0 isize, &'1 isize)>`, for any two lifetimes `'0` and `'1`... --> $DIR/associated-types-eq-hr.rs:59:8 | LL | fn tuple_one<T>() LL | where LL | T: for<'x, 'y> TheTrait<(&'x isize, &'y isize), A = &'x isize>, | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `tuple_one` note: ...but it actually implements `TheTrait<(&'2 isize, &'2 isize)>`, for some specific lifetime `'2` --> $DIR/associated-types-eq-hr.rs:35:1 | LL | impl<'a> TheTrait<(&'a isize, &'a isize)> for Tuple { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``` The output now is closer to what the next trait solver will emit (E0277).

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Comment thread compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/placeholder_error.rs Outdated

Comment thread compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs Outdated

rustbot 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 3, 2026

estebank added 5 commits October 3, 2026 17:27

Tweak wording

cf56d12

Remove redundant information

ca762cf

estebank force-pushed the not-general-enough branch from e114796 to 337f98d Compare October 3, 2026 17:28

rust-bors Bot 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 3, 2026

JonathanBrouwer mentioned this pull request Oct 3, 2026

Rollup of 6 pull requests #163718

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jhpratt mentioned this pull request Oct 3, 2026

Rollup of 18 pull requests #163729

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jhpratt mentioned this pull request Oct 4, 2026

Rollup of 18 pull requests #163735

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rust-bors Bot merged commit c49221b into rust-lang:main Oct 4, 2026
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rustbot added this to the 1.101.0 milestone Oct 4, 2026

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Tweak the rendering of "not general enough" errors on the old trait solver - #163613

Tweak the rendering of "not general enough" errors on the old trait solver#163613
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