Point at `'static` obligations from an fn being called by estebank · Pull Request #163115 · rust-lang/rust

estebank · 2026-09-21T14:59:47Z

Add this note to lifetime errors:

error[E0521]: borrowed data escapes outside of function
  --> $DIR/static-impl-obligation.rs:163:9
   |
LL |     fn bar<'a>(x: &'a &'a u32) {
   |            --  - `x` is only valid in the function body
   |            |
   |            lifetime `'a` defined here
LL |         let y: &dyn Foo = x;
LL |         y.hello();
   |         ^^^^^^^^^
   |         |
   |         `x` escapes the function body here
   |         argument requires that `'a` must outlive `'static`
   |
note: `'static` lifetime requirement from `<(dyn o::Foo + 'static)>::hello` introduced here
  --> $DIR/static-impl-obligation.rs:158:20
   |
LL |     impl dyn Foo + 'static where Self: 'static {
   |                    ^^^^^^^             ^^^^^^^ lifetime requirement introduced here
   |                    |
   |                    lifetime requirement introduced here
LL |         fn hello(&'static self) where Self: 'static {}
   |                  ^^^^^^^^^^^^^              ^^^^^^^ lifetime requirement introduced here
   |                  |
   |                  lifetime requirement introduced here

Follow up to #121274, taking only a subset of that unmerged PR's functionality.

rustbot · 2026-09-21T14:59:53Z

r? @davidtwco

rustbot has assigned @davidtwco.
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

Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: compiler
compiler expanded to 77 candidates
Random selection from 18 candidates

Add this note to lifetime errors: ```text error[E0521]: borrowed data escapes outside of function --> $DIR/static-impl-obligation.rs:163:9 | LL | fn bar<'a>(x: &'a &'a u32) { | -- - `x` is a reference that is only valid in the function body | | | lifetime `'a` defined here LL | let y: &dyn Foo = x; LL | y.hello(); | ^^^^^^^^^ | | | `x` escapes the function body here | argument requires that `'a` must outlive `'static` | note: `'static` requirement for `<(dyn o::Foo + 'static)>::hello` introduced here --> $DIR/static-impl-obligation.rs:158:40 | LL | impl dyn Foo + 'static where Self: 'static { | ^^^^^^^ `'static` requirement introduced here LL | fn hello(&'static self) where Self: 'static {} | ^^^^^^^ `'static` requirement introduced here ``` This currently only accounts for explicit bounds, other obligations like those arising from `Self` in a `impl dyn Trait {}` or from the receiver in `fn foo(&'static self)` are not accounted for.

rustbot · 2026-09-21T16:44:31Z

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.

``` note: `'static` lifetime requirement from `<(dyn b::Foo + 'static)>::hello` introduced here --> $DIR/static-impl-obligation.rs:16:18 | LL | impl dyn Foo { LL | fn hello(&'static self) {} | ^^^^^^^^^^^^^ lifetime requirement introduced here ```

``` note: `'static` lifetime requirement from `<(dyn a::Foo + 'static)>::hello` introduced here --> $DIR/static-impl-obligation.rs:4:5 | LL | impl dyn Foo { | ^^^^^^^^^^^^ lifetime requirement introduced here LL | fn hello(&self) {} | ```

… lifetime ``` note: `'static` lifetime requirement from `<(dyn a::Foo + 'static)>::hello` introduced here --> $DIR/static-impl-obligation.rs:4:10 | LL | impl dyn Foo { | ^^^^^^^ `dyn Trait` introduces an implicit `'static` lifetime requirement LL | fn hello(&self) {} | ``` ``` note: `'static` lifetime requirement from `<(dyn e::Foo + 'static)>::hello` introduced here --> $DIR/static-impl-obligation.rs:48:20 | LL | impl dyn Foo + 'static { | ^^^^^^^ lifetime requirement introduced here LL | fn hello(&self) {} | ```

rustbot · 2026-09-22T18:47:42Z

clippy is developed in its own repository. If possible, consider making this change to rust-lang/rust-clippy instead.

cc @rust-lang/clippy

estebank · 2026-09-22T18:50:17Z

+error[E0478]: lifetime bound not satisfied
+  --> $DIR/static-impl-obligation.rs:221:10
+   |
+LL |     impl MyTrait for dyn ObjectTrait + '_ {}
+   |          ^^^^^^^
+   |
+note: lifetime parameter instantiated with the anonymous lifetime as defined here
+  --> $DIR/static-impl-obligation.rs:221:40
+   |
+LL |     impl MyTrait for dyn ObjectTrait + '_ {}
+   |                                        ^^
+   = note: but lifetime parameter must outlive the static lifetime


Future work: This diagnostic should be pointing at 214 trait MyTrait where Self: 'static { as the reason why it must outlive 'static.

View changes since the review

estebank · 2026-09-22T18:52:18Z

+error[E0803]: cannot infer an appropriate lifetime for lifetime parameter `'_` due to conflicting requirements
+  --> $DIR/static-impl-obligation.rs:221:22
+   |
+LL |     impl MyTrait for dyn ObjectTrait + '_ {}
+   |                      ^^^^^^^^^^^^^^^^^^^^
+   |
+note: first, the lifetime cannot outlive the anonymous lifetime as defined here...
+  --> $DIR/static-impl-obligation.rs:221:40
+   |
+LL |     impl MyTrait for dyn ObjectTrait + '_ {}
+   |                                        ^^
+note: ...so that the types are compatible
+  --> $DIR/static-impl-obligation.rs:221:22
+   |
+LL |     impl MyTrait for dyn ObjectTrait + '_ {}
+   |                      ^^^^^^^^^^^^^^^^^^^^
+   = note: expected `<dyn t::ObjectTrait as t::MyTrait>`
+              found `<dyn t::ObjectTrait as t::MyTrait>`
+   = note: but, the lifetime must be valid for the static lifetime...
+note: ...so that the declared lifetime parameter bounds are satisfied
+  --> $DIR/static-impl-obligation.rs:221:22
+   |
+LL |     impl MyTrait for dyn ObjectTrait + '_ {}
+   |                      ^^^^^^^^^^^^^^^^^^^^


The second to last note should be pointing at 214.

View changes since the review

davidtwco · 2026-09-23T16:01:20Z

@bors r+ rollup

rust-bors · 2026-09-23T16:01:35Z

📌 Commit a91d256 has been approved by davidtwco

It is now in the queue for this repository.

…l, r=davidtwco Point at `'static` obligations from an fn being called Add this note to lifetime errors: ```text error[E0521]: borrowed data escapes outside of function --> $DIR/static-impl-obligation.rs:163:9 | LL | fn bar<'a>(x: &'a &'a u32) { | -- - `x` is only valid in the function body | | | lifetime `'a` defined here LL | let y: &dyn Foo = x; LL | y.hello(); | ^^^^^^^^^ | | | `x` escapes the function body here | argument requires that `'a` must outlive `'static` | note: `'static` lifetime requirement from `<(dyn o::Foo + 'static)>::hello` introduced here --> $DIR/static-impl-obligation.rs:158:20 | LL | impl dyn Foo + 'static where Self: 'static { | ^^^^^^^ ^^^^^^^ lifetime requirement introduced here | | | lifetime requirement introduced here LL | fn hello(&'static self) where Self: 'static {} | ^^^^^^^^^^^^^ ^^^^^^^ lifetime requirement introduced here | | | lifetime requirement introduced here ``` Follow up to rust-lang#121274, taking only a subset of that unmerged PR's functionality.

rustbot assigned davidtwco Sep 21, 2026

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 Sep 21, 2026

This comment has been minimized.

Sign in to view

estebank force-pushed the static-obligations-in-call branch from 6e47c50 to e478abb Compare September 21, 2026 16:44

estebank mentioned this pull request Sep 21, 2026

bad error message for missing static bounds on &dyn Trait #162882

Open

maxdexh reviewed Sep 21, 2026

View reviewed changes

Comment thread compiler/rustc_borrowck/src/diagnostics/region_errors.rs Outdated

estebank added 3 commits September 21, 2026 21:05

Point at 'static receiver

931b8bb

``` note: `'static` lifetime requirement from `<(dyn b::Foo + 'static)>::hello` introduced here --> $DIR/static-impl-obligation.rs:16:18 | LL | impl dyn Foo { LL | fn hello(&'static self) {} | ^^^^^^^^^^^^^ lifetime requirement introduced here ```

Point at impl dyn Trait 'static obligation

ffa9001

``` note: `'static` lifetime requirement from `<(dyn a::Foo + 'static)>::hello` introduced here --> $DIR/static-impl-obligation.rs:4:5 | LL | impl dyn Foo { | ^^^^^^^^^^^^ lifetime requirement introduced here LL | fn hello(&self) {} | ```

This comment has been minimized.

Sign in to view

estebank added 2 commits September 22, 2026 15:59

Fix test

94dc6dd

Update comment

a91d256

rustbot added the T-clippy Relevant to the Clippy team. label Sep 22, 2026

estebank commented Sep 22, 2026

View reviewed changes

davidtwco approved these changes Sep 23, 2026

View reviewed changes

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-review Status: Awaiting review from the assignee but also interested parties. labels Sep 23, 2026

rustbot mentioned this pull request Sep 23, 2026

Rollup of 10 pull requests #163227

Open

Navigation Menu

Uh oh!

Point at `'static` obligations from an fn being called - #163115

Point at `'static` obligations from an fn being called#163115
estebank wants to merge 6 commits into
rust-lang:mainfrom
estebank:static-obligations-in-call

estebank commented Sep 21, 2026 •

edited

Loading

Uh oh!

rustbot commented Sep 21, 2026

Uh oh!

This comment has been minimized.

rustbot commented Sep 21, 2026

Uh oh!

Uh oh!

This comment has been minimized.

rustbot commented Sep 22, 2026

Uh oh!

estebank Sep 22, 2026 •

edited by rustbot

Loading

Uh oh!

estebank Sep 22, 2026 •

edited by rustbot

Loading

Uh oh!

davidtwco commented Sep 23, 2026

Uh oh!

rust-bors Bot commented Sep 23, 2026

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

Uh oh!

Conversation

estebank commented Sep 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

rustbot commented Sep 21, 2026

Uh oh!

This comment has been minimized.

rustbot commented Sep 21, 2026

Uh oh!

Uh oh!

This comment has been minimized.

rustbot commented Sep 22, 2026

Uh oh!

estebank Sep 22, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

estebank Sep 22, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

davidtwco commented Sep 23, 2026

Uh oh!

rust-bors Bot commented Sep 23, 2026

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

estebank commented Sep 21, 2026 •

edited

Loading

estebank Sep 22, 2026 •

edited by rustbot

Loading

estebank Sep 22, 2026 •

edited by rustbot

Loading