Add `must_use` lint to `ExitCode` by ChrisDenton · Pull Request #162805 · rust-lang/rust

ChrisDenton · 2026-09-15T11:30:30Z

An ExitCode is intended to be returned from main (or used in other ways of terminating a process). It's also a Result like type in that it has success and error values. It's probably a mistake if it's ignored but if not it makes sense to require users to explicitly acknowledge that ignoring it is intentional (e.g. with let _ = ...).

rustbot · 2026-09-15T11:30:35Z

r? @jhpratt

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Owners of files modified in this PR: @ChrisDenton, libs
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jhpratt · 2026-09-16T18:54:47Z

@bors r+ rollup

rust-bors · 2026-09-16T18:54:50Z

📌 Commit 640d68d has been approved by jhpratt

It is now in the queue for this repository.

…jhpratt Add `must_use` lint to `ExitCode` An [`ExitCode`](https://doc.rust-lang.org/nightly/std/process/struct.ExitCode.html) is intended to be returned from `main` (or used in other ways of terminating a process). It's also a `Result` like type in that it has success and error values. It's *probably* a mistake if it's ignored but if not it makes sense to require users to explicitly acknowledge that ignoring it is intentional (e.g. with `let _ = ...`).

JonathanBrouwer · 2026-09-16T20:47:51Z

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #162866 (comment)

rust-bors · 2026-09-16T20:47:57Z

This pull request was unapproved.

This PR was contained in a rollup (#162866), which was unapproved.

View changes since this unapproval

ChrisDenton · 2026-09-16T22:03:22Z

@bors try jobs=test-aarch64-gnu-llvm-21-1

Add `must_use` lint to `ExitCode` try-job: test-aarch64-gnu-llvm-21-1

rust-bors · 2026-09-16T23:06:55Z

☀️ Try build successful (CI)
Build commit: e812626 (e812626eee6bfffcb1e8966dab34cafec9f50796)
Base parent: 923c95c (923c95cdf5ba65cea505aa2ea829f578e1506ed8)

ChrisDenton · 2026-09-16T23:07:53Z

Just a trivial test change to ignore the returned ExitCode in an attribute test.

@bors r=jhpratt

rust-bors · 2026-09-16T23:07:56Z

📌 Commit 99261fb has been approved by jhpratt

It is now in the queue for this repository.

…jhpratt Add `must_use` lint to `ExitCode` An [`ExitCode`](https://doc.rust-lang.org/nightly/std/process/struct.ExitCode.html) is intended to be returned from `main` (or used in other ways of terminating a process). It's also a `Result` like type in that it has success and error values. It's *probably* a mistake if it's ignored but if not it makes sense to require users to explicitly acknowledge that ignoring it is intentional (e.g. with `let _ = ...`).

Rollup of 12 pull requests Successful merges: - #161596 (coretests: Add more pattern tests.) - #162796 (libtest: do not early exit from test runners) - #162844 (Add loan reachability traces to polonius MIR dumps) - #158186 (Guarantee 8 bytes of alignment of RawWakerVTable) - #160108 (Stabilize `windows_process_extensions_main_thread_handle`) - #160212 (traits: Fix rigid alias liveness matching) - #160544 (Stabilize `feature(trim_prefix_suffix)` (`{str, [T], Path}::trim_prefix` and `{str, [T]}::trim_suffix`)) - #161305 (Use the entire type of a dropped local to compute variance (edge direction) for Polonius alpha) - #161838 (tests: accept LLVM 24 optimization in this test) - #162805 (Add `must_use` lint to `ExitCode`) - #162825 (core: Add examples for `debug_closure_helpers`) - #162856 (Stabilize CommandExt::show_window)

…jhpratt Add `must_use` lint to `ExitCode` An [`ExitCode`](https://doc.rust-lang.org/nightly/std/process/struct.ExitCode.html) is intended to be returned from `main` (or used in other ways of terminating a process). It's also a `Result` like type in that it has success and error values. It's *probably* a mistake if it's ignored but if not it makes sense to require users to explicitly acknowledge that ignoring it is intentional (e.g. with `let _ = ...`).

Rollup of 16 pull requests Successful merges: - #161596 (coretests: Add more pattern tests.) - #162796 (libtest: do not early exit from test runners) - #162844 (Add loan reachability traces to polonius MIR dumps) - #162876 (Move operations out of `rustc_middle::query::job`) - #160108 (Stabilize `windows_process_extensions_main_thread_handle`) - #160212 (traits: Fix rigid alias liveness matching) - #160544 (Stabilize `feature(trim_prefix_suffix)` (`{str, [T], Path}::trim_prefix` and `{str, [T]}::trim_suffix`)) - #161246 (Normalize non-rigid aliases in ty_known_to_outlive) - #161305 (Use the entire type of a dropped local to compute variance (edge direction) for Polonius alpha) - #161838 (tests: accept LLVM 24 optimization in this test) - #162805 (Add `must_use` lint to `ExitCode`) - #162825 (core: Add examples for `debug_closure_helpers`) - #162841 (enable asm tests for xtensa targets) - #162842 (reintroduce check RibKind::ConstParamTy did in direct consts) - #162845 (mgca: fix issue with mismatched array valtree/valtree tys) - #162856 (Stabilize CommandExt::show_window)

…jhpratt Add `must_use` lint to `ExitCode` An [`ExitCode`](https://doc.rust-lang.org/nightly/std/process/struct.ExitCode.html) is intended to be returned from `main` (or used in other ways of terminating a process). It's also a `Result` like type in that it has success and error values. It's *probably* a mistake if it's ignored but if not it makes sense to require users to explicitly acknowledge that ignoring it is intentional (e.g. with `let _ = ...`).

…uwer Rollup of 24 pull requests Successful merges: - #161596 (coretests: Add more pattern tests.) - #162177 (Properly implement the gpu-kernel ABI for amdgpu) - #162411 (Make Receiver `#[rustc_dyn_incompatible_trait]`) - #162760 (yeet alias new_from_def_id) - #162796 (libtest: do not early exit from test runners) - #162844 (Add loan reachability traces to polonius MIR dumps) - #162876 (Move operations out of `rustc_middle::query::job`) - #160108 (Stabilize `windows_process_extensions_main_thread_handle`) - #160212 (traits: Fix rigid alias liveness matching) - #160544 (Stabilize `feature(trim_prefix_suffix)` (`{str, [T], Path}::trim_prefix` and `{str, [T]}::trim_suffix`)) - #161305 (Use the entire type of a dropped local to compute variance (edge direction) for Polonius alpha) - #161838 (tests: accept LLVM 24 optimization in this test) - #162312 (core: Rewrite docs for try_as_dyn) - #162785 (Avoid creating overlapping assignments in MatchBranchSimplification) - #162805 (Add `must_use` lint to `ExitCode`) - #162825 (core: Add examples for `debug_closure_helpers`) - #162841 (enable asm tests for xtensa targets) - #162842 (reintroduce check RibKind::ConstParamTy did in direct consts) - #162845 (mgca: fix issue with mismatched array valtree/valtree tys) - #162856 (Stabilize CommandExt::show_window) - #162865 (Complex conjugate, negation and default) - #162874 (Add support for `annotate_snippets::snippet::AnnotationKind::Visible`) - #162881 (Simplify the macro for forwarding Decoder methods ) - #162888 (Fix a typo on the Armv7-R platform docs page)

…uwer Rollup of 23 pull requests Successful merges: - #161596 (coretests: Add more pattern tests.) - #162411 (Make Receiver `#[rustc_dyn_incompatible_trait]`) - #162760 (yeet alias new_from_def_id) - #162796 (libtest: do not early exit from test runners) - #162844 (Add loan reachability traces to polonius MIR dumps) - #162876 (Move operations out of `rustc_middle::query::job`) - #160108 (Stabilize `windows_process_extensions_main_thread_handle`) - #160212 (traits: Fix rigid alias liveness matching) - #160544 (Stabilize `feature(trim_prefix_suffix)` (`{str, [T], Path}::trim_prefix` and `{str, [T]}::trim_suffix`)) - #161305 (Use the entire type of a dropped local to compute variance (edge direction) for Polonius alpha) - #161838 (tests: accept LLVM 24 optimization in this test) - #162312 (core: Rewrite docs for try_as_dyn) - #162785 (Avoid creating overlapping assignments in MatchBranchSimplification) - #162805 (Add `must_use` lint to `ExitCode`) - #162825 (core: Add examples for `debug_closure_helpers`) - #162841 (enable asm tests for xtensa targets) - #162842 (reintroduce check RibKind::ConstParamTy did in direct consts) - #162845 (mgca: fix issue with mismatched array valtree/valtree tys) - #162856 (Stabilize CommandExt::show_window) - #162865 (Complex conjugate, negation and default) - #162874 (Add support for `annotate_snippets::snippet::AnnotationKind::Visible`) - #162881 (Simplify the macro for forwarding Decoder methods ) - #162888 (Fix a typo on the Armv7-R platform docs page)

Rollup merge of #162805 - ChrisDenton:exit-code-must-use, r=jhpratt Add `must_use` lint to `ExitCode` An [`ExitCode`](https://doc.rust-lang.org/nightly/std/process/struct.ExitCode.html) is intended to be returned from `main` (or used in other ways of terminating a process). It's also a `Result` like type in that it has success and error values. It's *probably* a mistake if it's ignored but if not it makes sense to require users to explicitly acknowledge that ignoring it is intentional (e.g. with `let _ = ...`).

rustbot assigned jhpratt Sep 15, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Sep 15, 2026

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 Sep 16, 2026

JonathanBrouwer mentioned this pull request Sep 16, 2026

Rollup of 9 pull requests #162866

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rust-bors Bot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Sep 16, 2026

Add must_use lint to ExitCode

99261fb

ChrisDenton force-pushed the exit-code-must-use branch from 640d68d to 99261fb Compare September 16, 2026 22:03

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rust-bors Bot pushed a commit that referenced this pull request Sep 16, 2026

Auto merge of #162805 - ChrisDenton:exit-code-must-use, r=<try>

e812626

Add `must_use` lint to `ExitCode` try-job: test-aarch64-gnu-llvm-21-1

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 16, 2026

Zalathar mentioned this pull request Sep 17, 2026

Rollup of 12 pull requests #162877

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Zalathar mentioned this pull request Sep 17, 2026

Rollup of 11 pull requests #162878

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Zalathar mentioned this pull request Sep 17, 2026

Rollup of 16 pull requests #162887

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JonathanBrouwer mentioned this pull request Sep 17, 2026

Rollup of 24 pull requests #162893

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JonathanBrouwer mentioned this pull request Sep 17, 2026

Rollup of 23 pull requests #162907

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rust-bors Bot merged commit b47b950 into rust-lang:main Sep 17, 2026
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rustbot added this to the 1.100.0 milestone Sep 17, 2026

ChrisDenton deleted the exit-code-must-use branch September 17, 2026 18:49

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Add `must_use` lint to `ExitCode` - #162805

Add `must_use` lint to `ExitCode`#162805
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