Handle generic reborrow in expression-use adjustment walking by P8L1 · Pull Request #156795 · rust-lang/rust

P8L1 · 2026-05-21T11:53:16Z

Fixes an ICE in expression-use adjustment walking where Adjust::GenericReborrow could reach a match arm that assumed generic reborrow was unreachable.

GenericReborrow is already emitted by typeck and classified as rvalue-producing elsewhere in expr_use_visitor.rs, so the adjustment walker must handle it explicitly instead of panicking.

This PR models GenericReborrow as a borrow-like use of the source expression:

Mutability::Mut is treated like an exclusive/mutable reborrow use.
Mutability::Not is treated like a shared/coerce-shared borrow-like use.
The source is not moved or treated as a mere copy.

cc @aapoalas
@rustbot label F-reborrow
Fixes #156339
Tracking: #145612

rustbot · 2026-05-21T11:53:21Z

r? @nikomatsakis

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aapoalas

LGTM.

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theemathas · 2026-05-21T13:12:53Z

Does this fix #156339 ?

P8L1 · 2026-05-21T19:01:02Z

Does this fix #156339 ?

Yes, this should fix #156339. I tested the repro from that issue on this branch: the Reborrow trait usage during adjustment walk ICE is gone. I also checked the old behavior by restoring the previous GenericReborrow unreachable in expr_use_visitor, and the repro hits the old ICE again there.

The reduced repro can still produce ordinary diagnostics unrelated to this PR, including the trait-method and async-block type errors from the issue, but the ICE from #156339 is the same expression-use GenericReborrow path and is fixed by this change.

aapoalas · 2026-05-22T09:25:55Z

r? @dingxiangfei2009

P8L1 · 2026-05-28T16:23:38Z

@bors squash

* Handle generic reborrow in expression-use adjustment walking * Require generic reborrow to be terminal in adjustment walks

rust-bors · 2026-05-28T16:24:17Z

🔨 2 commits were squashed into a5e4dc9.

dingxiangfei2009 · 2026-06-18T14:40:47Z

@P8L1 Thank you so much for contributing! With the flag implemented, indeed it matches the intention of the feature design.

@bors r+ rollup=always

rust-bors · 2026-06-18T14:40:55Z

📌 Commit a5e4dc9 has been approved by dingxiangfei2009

It is now in the queue for this repository.

@aapoalas

…-visitor, r=dingxiangfei2009 Handle generic reborrow in expression-use adjustment walking Fixes an ICE in expression-use adjustment walking where `Adjust::GenericReborrow` could reach a match arm that assumed generic reborrow was unreachable. `GenericReborrow` is already emitted by typeck and classified as rvalue-producing elsewhere in `expr_use_visitor.rs`, so the adjustment walker must handle it explicitly instead of panicking. This PR models `GenericReborrow` as a borrow-like use of the source expression: - `Mutability::Mut` is treated like an exclusive/mutable reborrow use. - `Mutability::Not` is treated like a shared/coerce-shared borrow-like use. - The source is not moved or treated as a mere copy. cc @aapoalas @rustbot label F-reborrow Fixes rust-lang#156339 Tracking: rust-lang#145612

@aapoalas

…-visitor, r=dingxiangfei2009 Handle generic reborrow in expression-use adjustment walking Fixes an ICE in expression-use adjustment walking where `Adjust::GenericReborrow` could reach a match arm that assumed generic reborrow was unreachable. `GenericReborrow` is already emitted by typeck and classified as rvalue-producing elsewhere in `expr_use_visitor.rs`, so the adjustment walker must handle it explicitly instead of panicking. This PR models `GenericReborrow` as a borrow-like use of the source expression: - `Mutability::Mut` is treated like an exclusive/mutable reborrow use. - `Mutability::Not` is treated like a shared/coerce-shared borrow-like use. - The source is not moved or treated as a mere copy. cc @aapoalas @rustbot label F-reborrow Fixes rust-lang#156339 Tracking: rust-lang#145612

…uwer Rollup of 6 pull requests Successful merges: - #158026 (`RegionValues`: disable unnecessary range check) - #156795 (Handle generic reborrow in expression-use adjustment walking) - #157694 (Enhance documentation on wake call memory ordering) - #158034 (Fix reborrow source expression visits) - #158074 (Document transient connection errors from TcpListener::accept) - #158086 (renovate: Loosen dashboard approval and adopt recommended config)

@aapoalas

…-visitor, r=dingxiangfei2009 Handle generic reborrow in expression-use adjustment walking Fixes an ICE in expression-use adjustment walking where `Adjust::GenericReborrow` could reach a match arm that assumed generic reborrow was unreachable. `GenericReborrow` is already emitted by typeck and classified as rvalue-producing elsewhere in `expr_use_visitor.rs`, so the adjustment walker must handle it explicitly instead of panicking. This PR models `GenericReborrow` as a borrow-like use of the source expression: - `Mutability::Mut` is treated like an exclusive/mutable reborrow use. - `Mutability::Not` is treated like a shared/coerce-shared borrow-like use. - The source is not moved or treated as a mere copy. cc @aapoalas @rustbot label F-reborrow Fixes rust-lang#156339 Tracking: rust-lang#145612

…uwer Rollup of 10 pull requests Successful merges: - #158026 (`RegionValues`: disable unnecessary range check) - #156795 (Handle generic reborrow in expression-use adjustment walking) - #157694 (Enhance documentation on wake call memory ordering) - #157935 (Make `proc_macro::ConversionErrorKind` non exhaustive) - #158002 (Replace `unwrap` with `expect` in `get_module_children`) - #158034 (Fix reborrow source expression visits) - #158072 (Bump thin-vec to 0.2.18 to address RUSTSEC-2026-0103) - #158074 (Document transient connection errors from TcpListener::accept) - #158077 (rustdoc-json-types: Replace bincode dev-dependency with postcard) - #158086 (renovate: Loosen dashboard approval and adopt recommended config)

Rollup of 12 pull requests Successful merges: - #156795 (Handle generic reborrow in expression-use adjustment walking) - #157694 (Enhance documentation on wake call memory ordering) - #157935 (Make `proc_macro::ConversionErrorKind` non exhaustive) - #158002 (Replace `unwrap` with `expect` in `get_module_children`) - #158009 (Reject `impl const Trait` since the right syntax is `const impl Trait` now) - #158034 (Fix reborrow source expression visits) - #158072 (Bump thin-vec to 0.2.18 to address RUSTSEC-2026-0103) - #158074 (Document transient connection errors from TcpListener::accept) - #158077 (rustdoc-json-types: Replace bincode dev-dependency with postcard) - #158086 (renovate: Loosen dashboard approval and adopt recommended config) - #158088 (codegen_ssa: no dbginfo for scalable vec local w/ `-O0`) - #158089 (Fix invalid "jump-to-def" doc link generation when an item has a `derive` proc-macro)

@aapoalas

Rollup merge of #156795 - P8L1:fix-generic-reborrow-expr-use-visitor, r=dingxiangfei2009 Handle generic reborrow in expression-use adjustment walking Fixes an ICE in expression-use adjustment walking where `Adjust::GenericReborrow` could reach a match arm that assumed generic reborrow was unreachable. `GenericReborrow` is already emitted by typeck and classified as rvalue-producing elsewhere in `expr_use_visitor.rs`, so the adjustment walker must handle it explicitly instead of panicking. This PR models `GenericReborrow` as a borrow-like use of the source expression: - `Mutability::Mut` is treated like an exclusive/mutable reborrow use. - `Mutability::Not` is treated like a shared/coerce-shared borrow-like use. - The source is not moved or treated as a mere copy. cc @aapoalas @rustbot label F-reborrow Fixes #156339 Tracking: #145612

Rollup of 12 pull requests Successful merges: - rust-lang/rust#156795 (Handle generic reborrow in expression-use adjustment walking) - rust-lang/rust#157694 (Enhance documentation on wake call memory ordering) - rust-lang/rust#157935 (Make `proc_macro::ConversionErrorKind` non exhaustive) - rust-lang/rust#158002 (Replace `unwrap` with `expect` in `get_module_children`) - rust-lang/rust#158009 (Reject `impl const Trait` since the right syntax is `const impl Trait` now) - rust-lang/rust#158034 (Fix reborrow source expression visits) - rust-lang/rust#158072 (Bump thin-vec to 0.2.18 to address RUSTSEC-2026-0103) - rust-lang/rust#158074 (Document transient connection errors from TcpListener::accept) - rust-lang/rust#158077 (rustdoc-json-types: Replace bincode dev-dependency with postcard) - rust-lang/rust#158086 (renovate: Loosen dashboard approval and adopt recommended config) - rust-lang/rust#158088 (codegen_ssa: no dbginfo for scalable vec local w/ `-O0`) - rust-lang/rust#158089 (Fix invalid "jump-to-def" doc link generation when an item has a `derive` proc-macro)

rustbot assigned nikomatsakis May 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 May 21, 2026

P8L1 force-pushed the fix-generic-reborrow-expr-use-visitor branch from 53084cc to 90709a5 Compare May 21, 2026 12:01

aapoalas approved these changes May 21, 2026

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Comment thread compiler/rustc_hir_typeck/src/expr_use_visitor.rs

rustbot assigned dingxiangfei2009 and unassigned nikomatsakis May 22, 2026

rustbot added the F-reborrow `#![feature(reborrow)]`; see #145612 label May 22, 2026

hbrooks mentioned this pull request May 28, 2026

Handle generic reborrow in expression-use adjustment walking ellipsis-dev-test/rust#4

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P8L1 requested a review from dingxiangfei2009 May 28, 2026 16:22

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Handle generic reborrow in expression-use adjustment walking

a5e4dc9

* Handle generic reborrow in expression-use adjustment walking * Require generic reborrow to be terminal in adjustment walks

rust-bors Bot force-pushed the fix-generic-reborrow-expr-use-visitor branch from 4b11926 to a5e4dc9 Compare May 28, 2026 16:24

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 Jun 18, 2026

jhpratt mentioned this pull request Jun 18, 2026

Rollup of 3 pull requests #158087

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JonathanBrouwer mentioned this pull request Jun 18, 2026

Rollup of 6 pull requests #158094

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JonathanBrouwer mentioned this pull request Jun 18, 2026

Rollup of 10 pull requests #158095

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GuillaumeGomez mentioned this pull request Jun 18, 2026

Rollup of 12 pull requests #158098

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rust-bors Bot merged commit 95cc3df into rust-lang:main Jun 18, 2026
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rustbot added this to the 1.98.0 milestone Jun 18, 2026

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Handle generic reborrow in expression-use adjustment walking#156795

Handle generic reborrow in expression-use adjustment walking#156795
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