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Suggest adding lifetime for dyn Trait in return type - #164188

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estebank:issue-41966
Oct 28, 2026
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Suggest adding lifetime for dyn Trait in return type#164188
rust-bors[bot] merged 1 commit into
rust-lang:mainfrom
estebank:issue-41966

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@estebank estebank commented Oct 12, 2026 •
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error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
help: consider adding an explicit lifetime bound
   |
LL | fn bb<'a, R>(r: R) -> Box<dyn Foo + 'a> {
   |       +++                         ++++

Address some cases from #41966.

@rustbot 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 Oct 12, 2026
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bushrat011899
bushrat011899 requested changes Oct 12, 2026
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Comment thread compiler/rustc_trait_selection/src/error_reporting/infer/region.rs Outdated
Comment thread compiler/rustc_trait_selection/src/error_reporting/infer/region.rs Outdated
Comment thread compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
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Reminder, once the PR becomes ready for a review, use @rustbot ready.

@estebank estebank added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 12, 2026
estebank
estebank commented Oct 12, 2026
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Comment thread tests/ui/suggestions/lifetimes/implicit-static-lifetime-in-dyn-trait-return-type.stderr
Comment on lines +49 to +56
help: consider adding an explicit lifetime bound
|
LL | fn baz<'a>(self) -> Box<dyn Baz + 'a> {
| ++++ ++++

@estebank estebank Oct 12, 2026 •
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This should probably go on the impl like the 'static suggestion...

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bushrat011899
bushrat011899 reviewed Oct 12, 2026
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This all looks good to me, but I'm not a member of the compiler team so I don't feel comfortable leaving an approval here. Thanks for answering the couple questions I had!

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@estebank
Suggest adding lifetime for dyn Trait in return type
da863f3 
```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound 3
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
help: consider adding an explicit lifetime bound
   |
LL | fn bb<'a, R>(r: R) -> Box<dyn Foo + 'a> {
   |       +++                         ++++
```
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rustbot commented Oct 23, 2026

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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.

@oli-obk

oli-obk commented Oct 27, 2026

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@bors r=bushrat011899,oli-obk

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📌 Commit da863f3 has been approved by bushrat011899,oli-obk

It is now in the queue for this repository.

@rust-bors 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 Oct 27, 2026
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Oct 27, 2026
@JonathanBrouwer
Rollup merge of rust-lang#164188 - estebank:issue-41966, r=bushrat011…
9fffcd4 
…899,oli-obk

Suggest adding lifetime for `dyn Trait` in return type

```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
help: consider adding an explicit lifetime bound
   |
LL | fn bb<'a, R>(r: R) -> Box<dyn Foo + 'a> {
   |       +++                         ++++
```

Address some cases from rust-lang#41966.
@JonathanBrouwer JonathanBrouwer mentioned this pull request Oct 27, 2026
Closed
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Oct 27, 2026
@JonathanBrouwer
Rollup merge of rust-lang#164188 - estebank:issue-41966, r=bushrat011…
004996c 
…899,oli-obk

Suggest adding lifetime for `dyn Trait` in return type

```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
help: consider adding an explicit lifetime bound
   |
LL | fn bb<'a, R>(r: R) -> Box<dyn Foo + 'a> {
   |       +++                         ++++
```

Address some cases from rust-lang#41966.
@JonathanBrouwer JonathanBrouwer mentioned this pull request Oct 27, 2026
Closed
rust-bors Bot pushed a commit that referenced this pull request Oct 27, 2026
@bors
Auto merge of #165051 - JonathanBrouwer:rollup-OlHxgXB, r=JonathanBro…
2e44078 
…uwer

Rollup of 22 pull requests

Successful merges:

 - #159580 (Reject cfg on expressions that cannot be safely removed)
 - #162597 (raise ambiguity error on attribute macro that could be tool attribute)
 - #162808 (Enable `--generate-link-to-definition` rustdoc option on std docs)
 - #163059 (Recover invalid return type until `{`, `}` or `;`)
 - #163672 (Use runCodeGen Abstraction for new LLVM)
 - #164028 (Add a future incompat warning for #[no_link])
 - #164188 (Suggest adding lifetime for `dyn Trait` in return type)
 - #164345 (fix: handle `false` in root contexts)
 - #164494 (drop ands which are a superset of other ands)
 - #164766 (Unstably introduce MVP edition migration lint `unmarked_unchecked_type_aliases` together with bikeshed attribute `#[rustc_unchecked_type_alias]`)
 - #164785 (delegation: emit error when there is no field for `Self` mapping)
 - #164799 (Don't use `IntoIterator` in parallel API)
 - #164871 (Refactor call argument codegen)
 - #164648 (parse inline and rustc_force_inline with same parser)
 - #164811 (fix: Prevent ICE when comparing EII impl against generic declaration)
 - #164900 (make tool_attrs method to retrieve tool attributes.)
 - #164993 (copy_nonoverlapping: dont skip ovelrap check when src is fully uninit)
 - #164996 (miri: add missing alignment check in write_bytes)
 - #165012 (Remove Span::eq_ctxt())
 - #165013 ([tiny] Add missing backticks around lifetime name)
 - #165024 (rustdoc-search: rank re-export lower)
 - #165028 (Update enzyme to fix one bug related to higher-order derivatives)

> [!WARNING]
> This rollup conflicts with pending auto build #165042 and may need to be recreated if the pending build succeeds.
@JonathanBrouwer JonathanBrouwer mentioned this pull request Oct 27, 2026
Merged
rust-bors Bot pushed a commit that referenced this pull request Oct 27, 2026
@bors
Auto merge of #165056 - JonathanBrouwer:rollup-ZFCUK9j, r=JonathanBro…
437bb0c 
…uwer

Rollup of 21 pull requests

Successful merges:

 - #159580 (Reject cfg on expressions that cannot be safely removed)
 - #162597 (raise ambiguity error on attribute macro that could be tool attribute)
 - #162808 (Enable `--generate-link-to-definition` rustdoc option on std docs)
 - #163059 (Recover invalid return type until `{`, `}` or `;`)
 - #163672 (Use runCodeGen Abstraction for new LLVM)
 - #164028 (Add a future incompat warning for #[no_link])
 - #164188 (Suggest adding lifetime for `dyn Trait` in return type)
 - #164345 (fix: handle `false` in root contexts)
 - #164494 (drop ands which are a superset of other ands)
 - #164785 (delegation: emit error when there is no field for `Self` mapping)
 - #164799 (Don't use `IntoIterator` in parallel API)
 - #164871 (Refactor call argument codegen)
 - #164648 (parse inline and rustc_force_inline with same parser)
 - #164811 (fix: Prevent ICE when comparing EII impl against generic declaration)
 - #164900 (make tool_attrs method to retrieve tool attributes.)
 - #164993 (copy_nonoverlapping: dont skip ovelrap check when src is fully uninit)
 - #164996 (miri: add missing alignment check in write_bytes)
 - #165012 (Remove Span::eq_ctxt())
 - #165013 ([tiny] Add missing backticks around lifetime name)
 - #165024 (rustdoc-search: rank re-export lower)
 - #165028 (Update enzyme to fix one bug related to higher-order derivatives)
rust-bors Bot pushed a commit that referenced this pull request Oct 28, 2026
@bors
Auto merge of #165056 - JonathanBrouwer:rollup-ZFCUK9j, r=JonathanBro…
0cf65bb 
…uwer

Rollup of 21 pull requests

Successful merges:

 - #159580 (Reject cfg on expressions that cannot be safely removed)
 - #162597 (raise ambiguity error on attribute macro that could be tool attribute)
 - #162808 (Enable `--generate-link-to-definition` rustdoc option on std docs)
 - #163059 (Recover invalid return type until `{`, `}` or `;`)
 - #163672 (Use runCodeGen Abstraction for new LLVM)
 - #164028 (Add a future incompat warning for #[no_link])
 - #164188 (Suggest adding lifetime for `dyn Trait` in return type)
 - #164345 (fix: handle `false` in root contexts)
 - #164494 (drop ands which are a superset of other ands)
 - #164785 (delegation: emit error when there is no field for `Self` mapping)
 - #164799 (Don't use `IntoIterator` in parallel API)
 - #164871 (Refactor call argument codegen)
 - #164648 (parse inline and rustc_force_inline with same parser)
 - #164811 (fix: Prevent ICE when comparing EII impl against generic declaration)
 - #164900 (make tool_attrs method to retrieve tool attributes.)
 - #164993 (copy_nonoverlapping: dont skip ovelrap check when src is fully uninit)
 - #164996 (miri: add missing alignment check in write_bytes)
 - #165012 (Remove Span::eq_ctxt())
 - #165013 ([tiny] Add missing backticks around lifetime name)
 - #165024 (rustdoc-search: rank re-export lower)
 - #165028 (Update enzyme to fix one bug related to higher-order derivatives)
rust-bors Bot pushed a commit that referenced this pull request Oct 28, 2026
@bors
Auto merge of #165056 - JonathanBrouwer:rollup-ZFCUK9j, r=JonathanBro…
f7ed956 
…uwer

Rollup of 21 pull requests

Successful merges:

 - #159580 (Reject cfg on expressions that cannot be safely removed)
 - #162597 (raise ambiguity error on attribute macro that could be tool attribute)
 - #162808 (Enable `--generate-link-to-definition` rustdoc option on std docs)
 - #163059 (Recover invalid return type until `{`, `}` or `;`)
 - #163672 (Use runCodeGen Abstraction for new LLVM)
 - #164028 (Add a future incompat warning for #[no_link])
 - #164188 (Suggest adding lifetime for `dyn Trait` in return type)
 - #164345 (fix: handle `false` in root contexts)
 - #164494 (drop ands which are a superset of other ands)
 - #164785 (delegation: emit error when there is no field for `Self` mapping)
 - #164799 (Don't use `IntoIterator` in parallel API)
 - #164871 (Refactor call argument codegen)
 - #164648 (parse inline and rustc_force_inline with same parser)
 - #164811 (fix: Prevent ICE when comparing EII impl against generic declaration)
 - #164900 (make tool_attrs method to retrieve tool attributes.)
 - #164993 (copy_nonoverlapping: dont skip ovelrap check when src is fully uninit)
 - #164996 (miri: add missing alignment check in write_bytes)
 - #165012 (Remove Span::eq_ctxt())
 - #165013 ([tiny] Add missing backticks around lifetime name)
 - #165024 (rustdoc-search: rank re-export lower)
 - #165028 (Update enzyme to fix one bug related to higher-order derivatives)
rust-bors Bot pushed a commit that referenced this pull request Oct 28, 2026
@bors
Auto merge of #165056 - JonathanBrouwer:rollup-ZFCUK9j, r=JonathanBro…
ab019e7 
…uwer

Rollup of 21 pull requests



Successful merges:

 - #159580 (Reject cfg on expressions that cannot be safely removed)
 - #162597 (raise ambiguity error on attribute macro that could be tool attribute)
 - #162808 (Enable `--generate-link-to-definition` rustdoc option on std docs)
 - #163059 (Recover invalid return type until `{`, `}` or `;`)
 - #163672 (Use runCodeGen Abstraction for new LLVM)
 - #164028 (Add a future incompat warning for #[no_link])
 - #164188 (Suggest adding lifetime for `dyn Trait` in return type)
 - #164345 (fix: handle `false` in root contexts)
 - #164494 (drop ands which are a superset of other ands)
 - #164785 (delegation: emit error when there is no field for `Self` mapping)
 - #164799 (Don't use `IntoIterator` in parallel API)
 - #164871 (Refactor call argument codegen)
 - #164648 (parse inline and rustc_force_inline with same parser)
 - #164811 (fix: Prevent ICE when comparing EII impl against generic declaration)
 - #164900 (make tool_attrs method to retrieve tool attributes.)
 - #164993 (copy_nonoverlapping: dont skip ovelrap check when src is fully uninit)
 - #164996 (miri: add missing alignment check in write_bytes)
 - #165012 (Remove Span::eq_ctxt())
 - #165013 ([tiny] Add missing backticks around lifetime name)
 - #165024 (rustdoc-search: rank re-export lower)
 - #165028 (Update enzyme to fix one bug related to higher-order derivatives)
@rust-bors
rust-bors Bot merged commit 40026d2 into rust-lang:main Oct 28, 2026
14 checks passed
@rustbot rustbot added this to the 1.101.0 milestone Oct 28, 2026
rust-bors Bot pushed a commit that referenced this pull request Oct 28, 2026
@bors
Unrolled build for #164188 in rollup 165056
1d74cb4 
Rollup merge of #164188 - estebank:issue-41966, r=bushrat011899,oli-obk

Suggest adding lifetime for `dyn Trait` in return type

```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
help: consider adding an explicit lifetime bound
   |
LL | fn bb<'a, R>(r: R) -> Box<dyn Foo + 'a> {
   |       +++                         ++++
```

Address some cases from #41966.
darkraider01 pushed a commit to darkraider01/miri that referenced this pull request Oct 29, 2026
@bors
Auto merge of #165056 - JonathanBrouwer:rollup-ZFCUK9j, r=JonathanBro…
1aff8cc 
…uwer

Rollup of 21 pull requests



Successful merges:

 - rust-lang/rust#159580 (Reject cfg on expressions that cannot be safely removed)
 - rust-lang/rust#162597 (raise ambiguity error on attribute macro that could be tool attribute)
 - rust-lang/rust#162808 (Enable `--generate-link-to-definition` rustdoc option on std docs)
 - rust-lang/rust#163059 (Recover invalid return type until `{`, `}` or `;`)
 - rust-lang/rust#163672 (Use runCodeGen Abstraction for new LLVM)
 - rust-lang/rust#164028 (Add a future incompat warning for #[no_link])
 - rust-lang/rust#164188 (Suggest adding lifetime for `dyn Trait` in return type)
 - rust-lang/rust#164345 (fix: handle `false` in root contexts)
 - rust-lang/rust#164494 (drop ands which are a superset of other ands)
 - rust-lang/rust#164785 (delegation: emit error when there is no field for `Self` mapping)
 - rust-lang/rust#164799 (Don't use `IntoIterator` in parallel API)
 - rust-lang/rust#164871 (Refactor call argument codegen)
 - rust-lang/rust#164648 (parse inline and rustc_force_inline with same parser)
 - rust-lang/rust#164811 (fix: Prevent ICE when comparing EII impl against generic declaration)
 - rust-lang/rust#164900 (make tool_attrs method to retrieve tool attributes.)
 - rust-lang/rust#164993 (copy_nonoverlapping: dont skip ovelrap check when src is fully uninit)
 - rust-lang/rust#164996 (miri: add missing alignment check in write_bytes)
 - rust-lang/rust#165012 (Remove Span::eq_ctxt())
 - rust-lang/rust#165013 ([tiny] Add missing backticks around lifetime name)
 - rust-lang/rust#165024 (rustdoc-search: rank re-export lower)
 - rust-lang/rust#165028 (Update enzyme to fix one bug related to higher-order derivatives)
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