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Cannot combine <code>async fn</code>-in-traits with <code>AsyncFn{,Mut}</code> closures

A-async-awaitArea: Async & AwaitArea: Async & Await

A-async-closures`async || {}``async || {}`

A-auto-traitsArea: auto traits (e.g., `auto trait Send {}`)Area: auto traits (e.g., `auto trait Send {}`)

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

C-bugCategory: This is a bug.Category: This is a bug.

fixed-by-higher-ranked-assumptionsFixed by `-Zhigher-ranked-assumptions`Fixed by `-Zhigher-ranked-assumptions`

Status: Open.

#145127 In rust-lang/rust;

· alexcrichton opened on Aug 8, 2025

Confusing lifetime error when using HRTB and closure

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-implied-boundsArea: Implied bounds / inferred outlives-boundsArea: Implied bounds / inferred outlives-bounds

C-bugCategory: This is a bug.Category: This is a bug.

needs-triageThis issue may need triage. Remove it if it has been sufficiently triaged.This issue may need triage. Remove it if it has been sufficiently triaged.

T-typesRelevant to the types team, which will review and decide on the PR/issue.Relevant to the types team, which will review and decide on the PR/issue.

Status: Open.

#143588 In rust-lang/rust;

· silver-ymz opened on Jul 7, 2025

Error points at <code>None</code> with implementation of <code>Fn</code> is not general enough

A-borrow-checkerArea: The borrow checkerArea: The borrow checker

A-diagnosticsArea: Messages for errors, warnings, and lintsArea: Messages for errors, warnings, and lints

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

D-imprecise-spansDiagnostics: spans don't point to exactly the erroneous codeDiagnostics: spans don't point to exactly the erroneous code

D-verboseDiagnostics: Too much output caused by a single piece of incorrect code.Diagnostics: Too much output caused by a single piece of incorrect code.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#143281 In rust-lang/rust;

· camsteffen opened on Jul 1, 2025

false positive : single-use-lifetimes <code>'_ is a reserved lifetime name</code>

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-lifetimesArea: Lifetimes / regionsArea: Lifetimes / regions

A-lintsArea: Lints (warnings about flaws in source code) such as unused_mut.Area: Lints (warnings about flaws in source code) such as unused_mut.

A-suggestion-diagnosticsArea: Suggestions generated by the compiler applied by `cargo fix`Area: Suggestions generated by the compiler applied by `cargo fix`

C-bugCategory: This is a bug.Category: This is a bug.

D-invalid-suggestionDiagnostics: A structured suggestion resulting in incorrect code.Diagnostics: A structured suggestion resulting in incorrect code.

L-false-positiveLint: False positive (should not have fired).Lint: False positive (should not have fired).

L-single_use_lifetimesLint: single_use_lifetimesLint: single_use_lifetimes

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#143131 In rust-lang/rust;

· matthiaskrgr opened on Jun 28, 2025

compiler gets stuck on recursive impl with duplicated for&lt;'a&gt; Trait bounds

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-trait-systemArea: Trait systemArea: Trait system

C-bugCategory: This is a bug.Category: This is a bug.

fixed-by-next-solverFixed by the next-generation trait solver, `-Znext-solver`.Fixed by the next-generation trait solver, `-Znext-solver`.

I-hangIssue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc.Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#142832 In rust-lang/rust;

· sososopy opened on Jun 21, 2025

Missing subtyping relationship between function pointers

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-lifetimesArea: Lifetimes / regionsArea: Lifetimes / regions

A-varianceArea: Variance (https://doc.rust-lang.org/nomicon/subtyping.html)Area: Variance (https://doc.rust-lang.org/nomicon/subtyping.html)

C-bugCategory: This is a bug.Category: This is a bug.

T-typesRelevant to the types team, which will review and decide on the PR/issue.Relevant to the types team, which will review and decide on the PR/issue.

Status: Open.

#142120 In rust-lang/rust;

· Jules-Bertholet opened on Jun 6, 2025

endless loop instead of an overflow error, in the presence of multiple requirements that would overflow.

A-GATsArea: Generic associated types (GATs)Area: Generic associated types (GATs)

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-trait-systemArea: Trait systemArea: Trait system

C-bugCategory: This is a bug.Category: This is a bug.

fixed-by-next-solverFixed by the next-generation trait solver, `-Znext-solver`.Fixed by the next-generation trait solver, `-Znext-solver`.

I-hangIssue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc.Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc.

T-typesRelevant to the types team, which will review and decide on the PR/issue.Relevant to the types team, which will review and decide on the PR/issue.

Status: Open.

#140946 In rust-lang/rust;

· moshevds opened on May 12, 2025

Error mentions invalid nested HRTB: <code>&amp;mut for&lt;'a&gt; fn(for&lt;'a&gt; fn(&amp;'a ()))</code>

A-diagnosticsArea: Messages for errors, warnings, and lintsArea: Messages for errors, warnings, and lints

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-prettyArea: Pretty printing (including `-Z unpretty`)Area: Pretty printing (including `-Z unpretty`)

D-incorrectDiagnostics: A diagnostic that is giving misleading or incorrect information.Diagnostics: A diagnostic that is giving misleading or incorrect information.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#134410 In rust-lang/rust;

· theemathas opened on Dec 17, 2024

Trait resolution fails, and then <code>rustc</code> hangs.

A-associated-itemsArea: Associated items (types, constants & functions)Area: Associated items (types, constants & functions)

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-trait-systemArea: Trait systemArea: Trait system

C-bugCategory: This is a bug.Category: This is a bug.

fixed-by-next-solverFixed by the next-generation trait solver, `-Znext-solver`.Fixed by the next-generation trait solver, `-Znext-solver`.

I-hangIssue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc.Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

T-typesRelevant to the types team, which will review and decide on the PR/issue.Relevant to the types team, which will review and decide on the PR/issue.

Status: Open.

#134312 In rust-lang/rust;

· frankmcsherry opened on Dec 14, 2024

<code>compare_method_predicate_entailment</code> is missing implied bounds from higher-ranked GAT

A-GATsArea: Generic associated types (GATs)Area: Generic associated types (GATs)

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-implied-boundsArea: Implied bounds / inferred outlives-boundsArea: Implied bounds / inferred outlives-bounds

A-trait-systemArea: Trait systemArea: Trait system

C-bugCategory: This is a bug.Category: This is a bug.

T-typesRelevant to the types team, which will review and decide on the PR/issue.Relevant to the types team, which will review and decide on the PR/issue.

Status: Open.

#133805 In rust-lang/rust;

· compiler-errors opened on Dec 3, 2024

Documentation uses HRTB lifetime before declaring it

A-cross-crate-reexportsArea: Documentation that has been re-exported from a different crateArea: Documentation that has been re-exported from a different crate

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

C-bugCategory: This is a bug.Category: This is a bug.

T-rustdocRelevant to the rustdoc team, which will review and decide on the PR/issue.Relevant to the rustdoc team, which will review and decide on the PR/issue.

Status: Open.

#132879 In rust-lang/rust;

· Scripter17 opened on Nov 10, 2024

Higher-ranked trait bounds in function signature incorrectly require bounds on the impl

A-associated-itemsArea: Associated items (types, constants & functions)Area: Associated items (types, constants & functions)

A-higher-rankedArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Area: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)

A-trait-systemArea: Trait systemArea: Trait system

C-bugCategory: This is a bug.Category: This is a bug.

fixed-by-next-solverFixed by the next-generation trait solver, `-Znext-solver`.Fixed by the next-generation trait solver, `-Znext-solver`.

T-typesRelevant to the types team, which will review and decide on the PR/issue.Relevant to the types team, which will review and decide on the PR/issue.

Status: Open.

#132089 In rust-lang/rust;

· 8000thCube opened on Oct 24, 2024