fix drop scope for `super let` bindings within `if let` #145342

dianne · 2025-08-13T08:40:59Z

Fixes #145328 by making non-lifetime-extended super let reuse the logic used to compute drop scopes for non-lifetime-extended temporaries.

Also fixes #145374, which regressed due to #143376 introducing if let-like scopes for match arms with guards.

Tracking issue for super let: #139076

This is a regression fix / breaking change for macros stably exposing super let, including pin! and format_args!.
Nominating to be discussed alongside #145328: @rustbot label +I-lang-nominated +I-libs-api-nominated

They now use the enclosing temporary scope as their scope, regardless of which `ScopeData` was used to mark it.

rustbot · 2025-08-13T08:41:03Z

r? @jackh726

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compiler-errors · 2025-08-13T14:58:23Z

@dianne does this need crater?

traviscross · 2025-08-13T15:38:36Z

@bors2 try

fix drop scope for `super let` bindings within `if let`

rust-bors · 2025-08-13T17:53:47Z

☀️ Try build successful (CI)
Build commit: a498031 (a4980311fb7bb9e7893708e6bd3fbbfb2819fd3d, parent: 350d0ef0ec0493e6d21cfb265cb8211a0e74d766)

compiler-errors · 2025-08-13T17:54:38Z

@craterbot check

craterbot · 2025-08-13T17:54:59Z

👌 Experiment pr-145342 created and queued.
🤖 Automatically detected try build a498031
🔍 You can check out the queue and this experiment's details.

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theemathas · 2025-08-14T03:10:58Z

How does #145374 relate to this? The code there doesn't use super let anywhere.

dianne · 2025-08-14T03:13:50Z

Format arguments, e.g. as used by write!, are also implemented in terms of super let. This is visible when printing the HIR of that test case:

f.write_fmt({
        super let args =
            (&pointee.behind_pointer(),
                &ItemIdentifier::path(&ItemIdentifier::nserror()));
        super let args =
            [format_argument::new_display(args.0),
                    format_argument::new_display(args.1)];
        format_arguments::new_v1(&["", ", "], &args)
    })

The interaction between that, old editions not treating block tail expressions as temporary drop scopes, my guard scoping PR, and the existing super let scoping bug is what caused that particular regression.

wesleywiser · 2025-08-28T14:13:06Z

r? rust-lang/compiler

rust-rfcbot · 2025-08-29T15:09:14Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

fee1-dead · 2025-09-01T19:32:02Z

r? rust-lang/compiler

nnethercote · 2025-09-03T11:48:42Z

@bors r+

bors · 2025-09-03T11:48:45Z

📌 Commit 8fc3938 has been approved by nnethercote

It is now in the queue for this repository.

…cote fix drop scope for `super let` bindings within `if let` Fixes rust-lang#145328 by making non-lifetime-extended `super let` reuse the logic used to compute drop scopes for non-lifetime-extended temporaries. Also fixes rust-lang#145374, which regressed due to rust-lang#143376 introducing `if let`-like scopes for match arms with guards. Tracking issue for `super let`: rust-lang#139076 This is a regression fix / breaking change for macros stably exposing `super let`, including `pin!` and `format_args!`. Nominating to be discussed alongside rust-lang#145328: `@rustbot` label +I-lang-nominated +I-libs-api-nominated

Rollup of 16 pull requests Successful merges: - #143725 (core: add Peekable::next_if_map) - #145209 (Stabilize `path_add_extension`) - #145342 (fix drop scope for `super let` bindings within `if let`) - #145750 (raw_vec.rs: Remove superfluous fn alloc_guard) - #145962 (Ensure we emit an allocator shim when only some crate types need one) - #145963 (Add LSX accelerated implementation for source file analysis) - #146054 (add `#[must_use]` to `array::repeat`) - #146090 (Derive `PartialEq` for `InvisibleOrigin`) - #146120 (Correct typo in `rustc_errors` comment) - #146127 (Rename `ToolRustc` to `ToolRustcPrivate`) - #146133 (Revert "Make `lto` and `linker-plugin-lto` work the same for `compiler_builtins`) - #146134 (llvm: nvptx: Layout update to match LLVM) - #146136 (docs(std): add missing closing code block fences in doc comments) - #146137 (Disallow frontmatter in `--cfg` and `--check-cfg` arguments) - #146140 (compiletest: cygwin follows windows in using PATH for dynamic libraries) - #146156 (miri subtree update) r? `@ghost` `@rustbot` modify labels: rollup

…cote fix drop scope for `super let` bindings within `if let` Fixes rust-lang#145328 by making non-lifetime-extended `super let` reuse the logic used to compute drop scopes for non-lifetime-extended temporaries. Also fixes rust-lang#145374, which regressed due to rust-lang#143376 introducing `if let`-like scopes for match arms with guards. Tracking issue for `super let`: rust-lang#139076 This is a regression fix / breaking change for macros stably exposing `super let`, including `pin!` and `format_args!`. Nominating to be discussed alongside rust-lang#145328: ``@rustbot`` label +I-lang-nominated +I-libs-api-nominated

Rollup of 24 pull requests Successful merges: - #140459 (Add `read_buf` equivalents for positioned reads) - #143725 (core: add Peekable::next_if_map) - #145209 (Stabilize `path_add_extension`) - #145342 (fix drop scope for `super let` bindings within `if let`) - #145750 (raw_vec.rs: Remove superfluous fn alloc_guard) - #145827 (On unused binding or binding not present in all patterns, suggest potential typo of unit struct/variant or const) - #145932 (Allow `inline(always)` with a target feature behind a unstable feature `target_feature_inline_always`.) - #145962 (Ensure we emit an allocator shim when only some crate types need one) - #145963 (Add LSX accelerated implementation for source file analysis) - #146054 (add `#[must_use]` to `array::repeat`) - #146090 (Derive `PartialEq` for `InvisibleOrigin`) - #146112 (don't uppercase error messages) - #146120 (Correct typo in `rustc_errors` comment) - #146124 (Test `rustc-dev` in `distcheck`) - #146127 (Rename `ToolRustc` to `ToolRustcPrivate`) - #146131 (rustdoc-search: add test case for indexing every item type) - #146134 (llvm: nvptx: Layout update to match LLVM) - #146136 (docs(std): add missing closing code block fences in doc comments) - #146137 (Disallow frontmatter in `--cfg` and `--check-cfg` arguments) - #146140 (compiletest: cygwin follows windows in using PATH for dynamic libraries) - #146150 (fix(rustdoc): match rustc `--emit` precedence ) - #146155 (Make bootstrap self test parallel) - #146161 ([rustdoc] Uncomment code to add scraped rustdoc examples in loaded paths) - #146172 (triagebot: configure some pings when certain attributes are used) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #145342 - dianne:if-let-super-let, r=nnethercote fix drop scope for `super let` bindings within `if let` Fixes #145328 by making non-lifetime-extended `super let` reuse the logic used to compute drop scopes for non-lifetime-extended temporaries. Also fixes #145374, which regressed due to #143376 introducing `if let`-like scopes for match arms with guards. Tracking issue for `super let`: #139076 This is a regression fix / breaking change for macros stably exposing `super let`, including `pin!` and `format_args!`. Nominating to be discussed alongside #145328: ```@rustbot``` label +I-lang-nominated +I-libs-api-nominated

apiraino · 2025-09-04T16:42:14Z

Beta backport declined as per compiler team on Zulip, we judge the backport a bit risky due to being about 2 weeks away from the new release.

@rustbot label -beta-nominated

Rollup of 24 pull requests Successful merges: - rust-lang/rust#140459 (Add `read_buf` equivalents for positioned reads) - rust-lang/rust#143725 (core: add Peekable::next_if_map) - rust-lang/rust#145209 (Stabilize `path_add_extension`) - rust-lang/rust#145342 (fix drop scope for `super let` bindings within `if let`) - rust-lang/rust#145750 (raw_vec.rs: Remove superfluous fn alloc_guard) - rust-lang/rust#145827 (On unused binding or binding not present in all patterns, suggest potential typo of unit struct/variant or const) - rust-lang/rust#145932 (Allow `inline(always)` with a target feature behind a unstable feature `target_feature_inline_always`.) - rust-lang/rust#145962 (Ensure we emit an allocator shim when only some crate types need one) - rust-lang/rust#145963 (Add LSX accelerated implementation for source file analysis) - rust-lang/rust#146054 (add `#[must_use]` to `array::repeat`) - rust-lang/rust#146090 (Derive `PartialEq` for `InvisibleOrigin`) - rust-lang/rust#146112 (don't uppercase error messages) - rust-lang/rust#146120 (Correct typo in `rustc_errors` comment) - rust-lang/rust#146124 (Test `rustc-dev` in `distcheck`) - rust-lang/rust#146127 (Rename `ToolRustc` to `ToolRustcPrivate`) - rust-lang/rust#146131 (rustdoc-search: add test case for indexing every item type) - rust-lang/rust#146134 (llvm: nvptx: Layout update to match LLVM) - rust-lang/rust#146136 (docs(std): add missing closing code block fences in doc comments) - rust-lang/rust#146137 (Disallow frontmatter in `--cfg` and `--check-cfg` arguments) - rust-lang/rust#146140 (compiletest: cygwin follows windows in using PATH for dynamic libraries) - rust-lang/rust#146150 (fix(rustdoc): match rustc `--emit` precedence ) - rust-lang/rust#146155 (Make bootstrap self test parallel) - rust-lang/rust#146161 ([rustdoc] Uncomment code to add scraped rustdoc examples in loaded paths) - rust-lang/rust#146172 (triagebot: configure some pings when certain attributes are used) r? `@ghost` `@rustbot` modify labels: rollup

dianne added 2 commits August 13, 2025 01:38

add a test with incorrect if let-super let drop order

bbf08d8

fix scope of super let bindings within if let

8fc3938

They now use the enclosing temporary scope as their scope, regardless of which `ScopeData` was used to mark it.

rustbot assigned jackh726 Aug 13, 2025

dianne force-pushed the if-let-super-let branch from f7b3d29 to 8fc3938 Compare August 13, 2025 08:41

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rust-bors bot added a commit that referenced this pull request Aug 13, 2025

Auto merge of #145342 - dianne:if-let-super-let, r=<try>

a498031

fix drop scope for `super let` bindings within `if let`

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 13, 2025

dianne mentioned this pull request Aug 14, 2025

Regression when dropping temporary value in match in older editions #145374

Closed

rustbot added the stable-nominated Nominated for backporting to the compiler in the stable channel. label Aug 14, 2025

compiler-errors added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Aug 14, 2025

traviscross added T-lang Relevant to the language team I-lang-radar Items that are on lang's radar and will need eventual work or consideration. and removed T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 14, 2025

rustbot assigned fee1-dead and unassigned jackh726 Aug 28, 2025

rustbot mentioned this pull request Aug 29, 2025

Tracking issue for release notes of #145342: fix drop scope for super let bindings within if let #146002

Open

dianne mentioned this pull request Sep 1, 2025

temporary lifetime extension for block tail expressions #146098

Draft

rustbot assigned nnethercote and unassigned fee1-dead Sep 1, 2025

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 Sep 3, 2025

Zalathar mentioned this pull request Sep 3, 2025

Rollup of 16 pull requests #146158

Closed

traviscross added the relnotes Marks issues that should be documented in the release notes of the next release. label Sep 3, 2025

Zalathar mentioned this pull request Sep 4, 2025

Rollup of 24 pull requests #146185

Merged

bors merged commit cd59ee7 into rust-lang:master Sep 4, 2025
11 checks passed

rustbot added this to the 1.91.0 milestone Sep 4, 2025

dianne deleted the if-let-super-let branch September 4, 2025 10:28

rustbot removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Sep 4, 2025

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