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Type inference tries to put the unsizing coercion in the wrong place

A-coercionsArea: implicit and explicit `expr as Type` coercionsArea: implicit and explicit `expr as Type` coercions

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

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.

#149881 In rust-lang/rust;

· RalfJung opened on Dec 11, 2025

Maybe-sized RPIT type is unexpectedly allowed in <code>async fn</code>

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

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

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

A-impl-traitArea: `impl Trait`. Universally / existentially quantified anonymous types with static dispatch.Area: `impl Trait`. Universally / existentially quantified anonymous types with static dispatch.

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.

#149438 In rust-lang/rust;

· obi1kenobi opened on Nov 29, 2025

Better Error for struct's with a field, that is DST, which is not the last

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

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

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

D-newcomer-roadblockDiagnostics: Confusing error or lint; hard to understand for new users.Diagnostics: Confusing error or lint; hard to understand for new users.

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.

#118522 In rust-lang/rust;

· C0D3-M4513R opened on Dec 1, 2023

trait object: specific use case of variance and/or coercion

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

A-dyn-traitArea: trait objects, vtable layoutArea: trait objects, vtable layout

A-trait-systemArea: Trait systemArea: Trait system

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

D-confusingDiagnostics: Confusing error or lint that should be reworked.Diagnostics: Confusing error or lint that should be reworked.

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.

#108999 In rust-lang/rust;

· plafer opened on Mar 10, 2023

Give a better error when an impl block implicitly requires <code>Sized</code>

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

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

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.

#98392 In rust-lang/rust;

· jyn514 opened on Jun 22, 2022

ptr-meta: DynMetadata and Pointee::Metadata are not UnwindSafe

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

A-lang-itemArea: Language itemsArea: Language items

A-raw-pointersArea: raw pointers, MaybeUninit, NonNullArea: raw pointers, MaybeUninit, NonNull

C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.

requires-nightlyThis issue requires a nightly compiler in some way. When possible, use a F-* label instead.This issue requires a nightly compiler in some way. When possible, use a F-* label instead.

T-libs-apiRelevant to the library API team, which will review and decide on the PR/issue.Relevant to the library API team, which will review and decide on the PR/issue.

Status: Open.

#86235 In rust-lang/rust;

· nwsharp opened on Jun 12, 2021

Functions, closures, and HRTB-trait-objects can implement traits such that validity of associated types is never checked.

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

A-closuresArea: Closures (`|…| { … }`)Area: Closures (`|…| { … }`)

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

A-dyn-traitArea: trait objects, vtable layoutArea: trait objects, vtable layout

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-trait-systemArea: Trait systemArea: Trait system

A-type-systemArea: Type systemArea: Type system

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

I-unsoundIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/SoundnessIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness

P-mediumMedium priorityMedium priority

S-bug-has-testStatus: This bug is tracked inside the repo by a `known-bug` test.Status: This bug is tracked inside the repo by a `known-bug` test.

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.

#84533 In rust-lang/rust;

· steffahn opened on Apr 24, 2021

Destructor of one struct field depends on other without any correlation

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

A-lifetimesArea: Lifetimes / regionsArea: Lifetimes / regions

A-trait-systemArea: Trait systemArea: Trait system

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

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.

#78940 In rust-lang/rust;

· MihirLuthra opened on Nov 11, 2020

Provide suggestion on E0277 Sized error when <code>&amp;**</code>/<code>as_ref()</code> would be appropriate

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

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

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

C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.

D-newcomer-roadblockDiagnostics: Confusing error or lint; hard to understand for new users.Diagnostics: Confusing error or lint; hard to understand for new users.

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.

#77588 In rust-lang/rust;

· estebank opened on Oct 5, 2020

Problem with <code>PartialEq</code>

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

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

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.

#67369 In rust-lang/rust;

· zakarumych opened on Dec 17, 2019

E0119 can overwrite E0277 leading to confusing error message

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

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

D-papercutDiagnostics: An error or lint that needs small tweaks.Diagnostics: An error or lint that needs small tweaks.

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.

#66712 In rust-lang/rust;

· CAD97 opened on Nov 24, 2019

Confusing behavior around unsized return values in traits

A-DSTsArea: Dynamically-sized types (DSTs)Area: Dynamically-sized types (DSTs)

A-trait-systemArea: Trait systemArea: Trait system

C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.

T-langRelevant to the language teamRelevant to the language team

Status: Open.

#51784 In rust-lang/rust;

· RalfJung opened on Jun 25, 2018