Avoid incorrect lifetime suggestion involving `sym::anon` by estebank · Pull Request #148842 · rust-lang/rust

estebank · 2025-11-11T22:40:30Z

Given

#!/usr/bin/env -S cargo +nightly -Zscript -q
---
packag.edition = "2024"

[dependencies]
rama = "0.2.0"
---

fn main() {}

struct Foo;

impl<S, Request: 'static> rama::Service<S, Request> for Foo {
    type Response = ();
    type Error = ();

    fn serve(
        &self,
        _ctx: rama::Context<S>,
        _req: Request,
    ) -> impl Future<Output = Result<Self::Response, Self::Error>> {
        async { todo!() }
    }
}

emit

error[E0311]: the parameter type `S` may not live long enough
  --> f20.rs:20:10
   |
20 |     ) -> impl Future<Output = Result<Self::Response, Self::Error>> {
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Result<<Foo as Service<S, Request>>::Response, <Foo as Service<S, Request>>::Error>>` will meet its required lifetime bounds...
   |
  ::: /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:19:9
   |
19 |         &self,
   |         - the parameter type `S` must be valid for the anonymous lifetime as defined here...
   |
note: ...that is required by this bound
  --> /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:22:77
   |
22 |     ) -> impl Future<Output = Result<Self::Response, Self::Error>> + Send + '_;
   |                                                                             ^^

without the incorrect suggestion

help: consider adding an explicit lifetime bound
   |
22 |     ) -> impl Future<Output = Result<Self::Response, Self::Error>> where S: anon {
   |                                                                    +++++++++++++

Address #142887. Needs a repro test.

rustbot · 2025-11-11T22:40:35Z

r? @nnethercote

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nnethercote

Needs a repro test.

Yes!

View changes since this review

JayanAXHF · 2026-02-13T12:08:05Z

@estebank Hi Triage here, is there anything blocking this PRs implementation? Are you still working on this?

estebank · 2026-02-13T18:03:06Z

@JayanAXHF I need to come up with a minimized repro case that's suitable for the test suite. I could do with an extra hand on that.

JayanAXHF · 2026-02-13T18:20:23Z

Ive added the E-needs-mcve label, hopefully the CFP works!

rustbot · 2026-10-18T19:55:29Z

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.

Invalid lifetime suggested: ``` error[E0311]: the parameter type `S` may not live long enough --> $DIR/do-not-suggest-anon-lifetime.rs:16:10 | LL | ) -> impl Future<Output = Result<Self::Response, Self::Error>> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Result<<Foo as Service<S, Request>>::Response, <Foo as Service<S, Request>>::Error>>` will meet its required lifetime bounds... | ::: $DIR/auxiliary/anon_lifetime.rs:14:9 | LL | &self, | - the parameter type `S` must be valid for the anonymous lifetime as defined here... | note: ...that is required by this bound --> $DIR/auxiliary/anon_lifetime.rs:17:77 | LL | ) -> impl Future<Output = Result<Self::Response, Self::Error>> + Send + '_; | ^^ help: consider adding an explicit lifetime bound | LL | ) -> impl Future<Output = Result<Self::Response, Self::Error>> where S: anon { | +++++++++++++ ```

Given ```rust --- packag.edition = "2024" [dependencies] rama = "0.2.0" --- fn main() {} struct Foo; impl<S, Request: 'static> rama::Service<S, Request> for Foo { type Response = (); type Error = (); fn serve( &self, _ctx: rama::Context<S>, _req: Request, ) -> impl Future<Output = Result<Self::Response, Self::Error>> { async { todo!() } } } ``` emit ``` error[E0311]: the parameter type `S` may not live long enough --> f20.rs:20:10 | 20 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Result<<Foo as Service<S, Request>>::Response, <Foo as Service<S, Request>>::Error>>` will meet its required lifetime bounds... | ::: /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:19:9 | 19 | &self, | - the parameter type `S` must be valid for the anonymous lifetime as defined here... | note: ...that is required by this bound --> /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:22:77 | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> + Send + '_; | ^^ ``` without the incorrect suggestion ``` help: consider adding an explicit lifetime bound | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> where S: anon { | +++++++++++++ ```

nnethercote · 2026-10-20T13:06:04Z

get_name_or_anon is a really weird function.

@bors r+ rollup

rust-bors · 2026-10-20T13:06:08Z

📌 Commit 0a5b761 has been approved by nnethercote

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 5. This pull request will be tested once the tree is reopened.

Reason for tree closure: spurious failures

Avoid incorrect lifetime suggestion involving `sym::anon` Given ```rust #!/usr/bin/env -S cargo +nightly -Zscript -q --- packag.edition = "2024" [dependencies] rama = "0.2.0" --- fn main() {} struct Foo; impl<S, Request: 'static> rama::Service<S, Request> for Foo { type Response = (); type Error = (); fn serve( &self, _ctx: rama::Context<S>, _req: Request, ) -> impl Future<Output = Result<Self::Response, Self::Error>> { async { todo!() } } } ``` emit ``` error[E0311]: the parameter type `S` may not live long enough --> f20.rs:20:10 | 20 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Result<<Foo as Service<S, Request>>::Response, <Foo as Service<S, Request>>::Error>>` will meet its required lifetime bounds... | ::: /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:19:9 | 19 | &self, | - the parameter type `S` must be valid for the anonymous lifetime as defined here... | note: ...that is required by this bound --> /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:22:77 | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> + Send + '_; | ^^ ``` without the incorrect suggestion ``` help: consider adding an explicit lifetime bound | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> where S: anon { | +++++++++++++ ``` Address rust-lang#142887. Needs a repro test.

…uwer Rollup of 15 pull requests Successful merges: - #163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - #163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - #163338 (MIR move elimination [4/6]: MoveElimination) - #163701 (add ReadDir::dir to get the directory handle of the underlying directory) - #164488 (Don't try to skip anything in `Skip::advance_by(0)`) - #164611 (Improve bit permutation codegen) - #164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - #148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - #162668 (document that `!` does bitwise and logical negation) - #164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - #164509 (layout invariant: turn delayed bug back into proper assertion) - #164540 (Minor optimizations around macro parsing) - #164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - #164595 (Allow attributes in function trait parameters) - #164629 (arch::breakpoint: avoid confusing 'equivalent' terminology)

Avoid incorrect lifetime suggestion involving `sym::anon` Given ```rust #!/usr/bin/env -S cargo +nightly -Zscript -q --- packag.edition = "2024" [dependencies] rama = "0.2.0" --- fn main() {} struct Foo; impl<S, Request: 'static> rama::Service<S, Request> for Foo { type Response = (); type Error = (); fn serve( &self, _ctx: rama::Context<S>, _req: Request, ) -> impl Future<Output = Result<Self::Response, Self::Error>> { async { todo!() } } } ``` emit ``` error[E0311]: the parameter type `S` may not live long enough --> f20.rs:20:10 | 20 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Result<<Foo as Service<S, Request>>::Response, <Foo as Service<S, Request>>::Error>>` will meet its required lifetime bounds... | ::: /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:19:9 | 19 | &self, | - the parameter type `S` must be valid for the anonymous lifetime as defined here... | note: ...that is required by this bound --> /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:22:77 | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> + Send + '_; | ^^ ``` without the incorrect suggestion ``` help: consider adding an explicit lifetime bound | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> where S: anon { | +++++++++++++ ``` Address rust-lang#142887. Needs a repro test.

…uwer Rollup of 14 pull requests Successful merges: - #163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - #163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - #163701 (add ReadDir::dir to get the directory handle of the underlying directory) - #164488 (Don't try to skip anything in `Skip::advance_by(0)`) - #164611 (Improve bit permutation codegen) - #164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - #148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - #162668 (document that `!` does bitwise and logical negation) - #164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - #164509 (layout invariant: turn delayed bug back into proper assertion) - #164540 (Minor optimizations around macro parsing) - #164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - #164595 (Allow attributes in function trait parameters) - #164629 (arch::breakpoint: avoid confusing 'equivalent' terminology)

Avoid incorrect lifetime suggestion involving `sym::anon` Given ```rust #!/usr/bin/env -S cargo +nightly -Zscript -q --- packag.edition = "2024" [dependencies] rama = "0.2.0" --- fn main() {} struct Foo; impl<S, Request: 'static> rama::Service<S, Request> for Foo { type Response = (); type Error = (); fn serve( &self, _ctx: rama::Context<S>, _req: Request, ) -> impl Future<Output = Result<Self::Response, Self::Error>> { async { todo!() } } } ``` emit ``` error[E0311]: the parameter type `S` may not live long enough --> f20.rs:20:10 | 20 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Result<<Foo as Service<S, Request>>::Response, <Foo as Service<S, Request>>::Error>>` will meet its required lifetime bounds... | ::: /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:19:9 | 19 | &self, | - the parameter type `S` must be valid for the anonymous lifetime as defined here... | note: ...that is required by this bound --> /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:22:77 | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> + Send + '_; | ^^ ``` without the incorrect suggestion ``` help: consider adding an explicit lifetime bound | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> where S: anon { | +++++++++++++ ``` Address rust-lang#142887. Needs a repro test.

…uwer Rollup of 19 pull requests Successful merges: - #163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - #163668 (Remap syntax contexts and expansion ids for det. metadata encoding) - #160404 (fd-views: AsRef<File>&Co. for BorrowedFd) - #163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - #163317 (Stop useless caching of post-LTO artifact caching for fat LTO) - #163701 (add ReadDir::dir to get the directory handle of the underlying directory) - #164488 (Don't try to skip anything in `Skip::advance_by(0)`) - #164507 (Encode HashMap and HashSet in deterministic order when an encoder requires determinism) - #164611 (Improve bit permutation codegen) - #164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - #148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - #162668 (document that `!` does bitwise and logical negation) - #164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - #164509 (layout invariant: turn delayed bug back into proper assertion) - #164540 (Minor optimizations around macro parsing) - #164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - #164595 (Allow attributes in function trait parameters) - #164641 (Stabilize `slice_split_once`) - #164646 (Adjust rustfmt subtree sync docs to not use `--allow-noop` for now)

Rollup of 20 pull requests Successful merges: - #163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - #163668 (Remap syntax contexts and expansion ids for det. metadata encoding) - #163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - #163317 (Stop useless caching of post-LTO artifact caching for fat LTO) - #163701 (add ReadDir::dir to get the directory handle of the underlying directory) - #164488 (Don't try to skip anything in `Skip::advance_by(0)`) - #164507 (Encode HashMap and HashSet in deterministic order when an encoder requires determinism) - #164611 (Improve bit permutation codegen) - #164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - #148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - #162668 (document that `!` does bitwise and logical negation) - #164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - #164509 (layout invariant: turn delayed bug back into proper assertion) - #164540 (Minor optimizations around macro parsing) - #164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - #164595 (Allow attributes in function trait parameters) - #164616 (Add test for VecDeque with a custom allocator) - #164629 (arch::breakpoint: avoid confusing 'equivalent' terminology) - #164641 (Stabilize `slice_split_once`) - #164646 (Adjust rustfmt subtree sync docs to not use `--allow-noop` for now)

Rollup merge of #148842 - estebank:issue-142887, r=nnethercote Avoid incorrect lifetime suggestion involving `sym::anon` Given ```rust #!/usr/bin/env -S cargo +nightly -Zscript -q --- packag.edition = "2024" [dependencies] rama = "0.2.0" --- fn main() {} struct Foo; impl<S, Request: 'static> rama::Service<S, Request> for Foo { type Response = (); type Error = (); fn serve( &self, _ctx: rama::Context<S>, _req: Request, ) -> impl Future<Output = Result<Self::Response, Self::Error>> { async { todo!() } } } ``` emit ``` error[E0311]: the parameter type `S` may not live long enough --> f20.rs:20:10 | 20 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Result<<Foo as Service<S, Request>>::Response, <Foo as Service<S, Request>>::Error>>` will meet its required lifetime bounds... | ::: /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:19:9 | 19 | &self, | - the parameter type `S` must be valid for the anonymous lifetime as defined here... | note: ...that is required by this bound --> /home/gh-estebank/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rama-core-0.2.0/src/service/svc.rs:22:77 | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> + Send + '_; | ^^ ``` without the incorrect suggestion ``` help: consider adding an explicit lifetime bound | 22 | ) -> impl Future<Output = Result<Self::Response, Self::Error>> where S: anon { | +++++++++++++ ``` Address #142887. Needs a repro test.

Rollup of 20 pull requests Successful merges: - rust-lang/rust#163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - rust-lang/rust#163668 (Remap syntax contexts and expansion ids for det. metadata encoding) - rust-lang/rust#163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - rust-lang/rust#163317 (Stop useless caching of post-LTO artifact caching for fat LTO) - rust-lang/rust#163701 (add ReadDir::dir to get the directory handle of the underlying directory) - rust-lang/rust#164488 (Don't try to skip anything in `Skip::advance_by(0)`) - rust-lang/rust#164507 (Encode HashMap and HashSet in deterministic order when an encoder requires determinism) - rust-lang/rust#164611 (Improve bit permutation codegen) - rust-lang/rust#164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - rust-lang/rust#148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - rust-lang/rust#162668 (document that `!` does bitwise and logical negation) - rust-lang/rust#164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - rust-lang/rust#164509 (layout invariant: turn delayed bug back into proper assertion) - rust-lang/rust#164540 (Minor optimizations around macro parsing) - rust-lang/rust#164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - rust-lang/rust#164595 (Allow attributes in function trait parameters) - rust-lang/rust#164616 (Add test for VecDeque with a custom allocator) - rust-lang/rust#164629 (arch::breakpoint: avoid confusing 'equivalent' terminology) - rust-lang/rust#164641 (Stabilize `slice_split_once`) - rust-lang/rust#164646 (Adjust rustfmt subtree sync docs to not use `--allow-noop` for now)

rustbot assigned nnethercote Nov 11, 2025

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JayanAXHF added the E-needs-mcve Call for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example label Feb 13, 2026

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Rollup of 15 pull requests #164639

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Rollup of 14 pull requests #164640

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Rollup of 19 pull requests #164658

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Rollup of 20 pull requests #164662

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Toolchain upgrade to nightly-2026-10-22 flux-rs/flux#1847

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Avoid incorrect lifetime suggestion involving `sym::anon` - #148842

Avoid incorrect lifetime suggestion involving `sym::anon`#148842
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