Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std by estebank · Pull Request #149795 · rust-lang/rust

estebank · 2025-12-09T00:10:42Z

Split off #148837.

rustbot · 2025-12-09T00:10:46Z

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workingjubilee

some of these format kinda weirdly.

View changes since this review

workingjubilee · 2025-12-09T03:02:48Z

library/core/src/time.rs

-                if let Some(new_secs) = secs.checked_add(1) {
-                    secs = new_secs;
-                } else {
-                    return None;
-                }
+                let Some(new_secs) = secs.checked_add(1) else { return None };
+                secs = new_secs;


I feel it is much harder to read the control flow in this case because we have hidden the return off to the right.

workingjubilee · 2025-12-09T03:03:36Z

library/alloc/src/string.rs

-            } else {
-                return Err(FromUtf16Error(()));
-            }
+            let Ok(c) = c else { return Err(FromUtf16Error(())) };


This also loses clarity due to let-else, IMO.

Would you be ok with the let...else if the return block was on its own line?

basically yes.

workingjubilee · 2025-12-09T04:01:18Z

library/alloc/src/raw_vec/mod.rs

-        let (ptr, layout) = if let Some(mem) = unsafe { self.current_memory(elem_layout) } {
-            mem
-        } else {
+        let Some((ptr, layout)) = (unsafe { self.current_memory(elem_layout) }) else {


this is obviously fine, to be clear.

…f let ... else return` in std

workingjubilee · 2025-12-10T03:02:36Z

it's so weird to me that that matters. oh well.

workingjubilee · 2025-12-10T03:03:13Z

@bors r+ rollup

bors · 2025-12-10T03:03:16Z

📌 Commit 0488690 has been approved by workingjubilee

It is now in the queue for this repository.

…bilee Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std Split off rust-lang#148837.

Rollup of 12 pull requests Successful merges: - #147602 (Deduplicate higher-ranked lifetime capture errors in impl Trait) - #147725 (Remove -Zoom=panic) - #148294 (callconv: fix mips64 aggregate argument passing for C FFI) - #148491 ( Correctly provide suggestions when encountering `async fn` with a `dyn Trait` return type) - #149417 (tidy: Detect outdated workspaces in workspace list) - #149458 (Run clippy on cg_gcc in CI) - #149679 (Restrict spe_acc to PowerPC SPE targets) - #149781 (Don't suggest wrapping attr in unsafe if it may come from proc macro) - #149795 (Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std) - #149816 (Make typo in field and name suggestions verbose) - #149824 (Add a regression test for issue 145748) - #149826 (compiletest: tidy up `adb_path`/`adb_test_dir` handling) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 10 pull requests Successful merges: - #147725 (Remove -Zoom=panic) - #148294 (callconv: fix mips64 aggregate argument passing for C FFI) - #148491 ( Correctly provide suggestions when encountering `async fn` with a `dyn Trait` return type) - #149458 (Run clippy on cg_gcc in CI) - #149679 (Restrict spe_acc to PowerPC SPE targets) - #149781 (Don't suggest wrapping attr in unsafe if it may come from proc macro) - #149795 (Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std) - #149816 (Make typo in field and name suggestions verbose) - #149824 (Add a regression test for issue 145748) - #149826 (compiletest: tidy up `adb_path`/`adb_test_dir` handling) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #149795 - estebank:let-else-std, r=workingjubilee Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std Split off #148837.

Rollup of 10 pull requests Successful merges: - rust-lang/rust#147725 (Remove -Zoom=panic) - rust-lang/rust#148294 (callconv: fix mips64 aggregate argument passing for C FFI) - rust-lang/rust#148491 ( Correctly provide suggestions when encountering `async fn` with a `dyn Trait` return type) - rust-lang/rust#149458 (Run clippy on cg_gcc in CI) - rust-lang/rust#149679 (Restrict spe_acc to PowerPC SPE targets) - rust-lang/rust#149781 (Don't suggest wrapping attr in unsafe if it may come from proc macro) - rust-lang/rust#149795 (Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std) - rust-lang/rust#149816 (Make typo in field and name suggestions verbose) - rust-lang/rust#149824 (Add a regression test for issue 145748) - rust-lang/rust#149826 (compiletest: tidy up `adb_path`/`adb_test_dir` handling) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned Mark-Simulacrum Dec 9, 2025

rustbot added O-windows Operating system: Windows 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 Dec 9, 2025

workingjubilee reviewed Dec 9, 2025

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estebank force-pushed the let-else-std branch from 698ff18 to 0ab59e7 Compare December 9, 2025 23:22

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Use let...else instead of match foo { ... _ => return }; and `i…

0488690

…f let ... else return` in std

estebank force-pushed the let-else-std branch from 0ab59e7 to 0488690 Compare December 9, 2025 23:35

bors 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 Dec 10, 2025

Zalathar mentioned this pull request Dec 10, 2025

Rollup of 13 pull requests #149828

Closed

Zalathar mentioned this pull request Dec 10, 2025

Rollup of 12 pull requests #149830

Closed

matthiaskrgr mentioned this pull request Dec 10, 2025

Rollup of 10 pull requests #149836

Merged

bors merged commit 3a3c7b5 into rust-lang:main Dec 10, 2025
11 checks passed

rustbot added this to the 1.94.0 milestone Dec 10, 2025

rust-timer added a commit that referenced this pull request Dec 10, 2025

Unrolled build for #149795

c2d36f8

Rollup merge of #149795 - estebank:let-else-std, r=workingjubilee Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std Split off #148837.

github-actions bot mentioned this pull request Dec 12, 2025

Toolchain upgrade to nightly-2026-01-30 flux-rs/flux#1345

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Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std#149795

Use `let`...`else` instead of `match foo { ... _ => return };` and `if let ... else return` in std#149795
bors merged 1 commit intorust-lang:mainfrom
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