Adjust spans into the `for` loops context before creating the new desugaring spans. by Jarcho · Pull Request #148465 · rust-lang/rust

Jarcho · 2025-11-04T08:14:58Z

When lowering for loops, the spans for the into_iter call and the Some pattern used the span of the provided pattern and head expression. If either of those came from a different SyntaxContext this would result in some very strange contexts. e.g.:

macro_rules! m { ($e:expr) => { { $e } } }
for _ in m!(expr) {}

This would result in the into_iter call have a context chain of desugar => m!() => root which is completely nonsensical; m!() does not have a for loop. The into_iter call also ends up located at { $e } rather than inside the for _ in _ part.

This fixes that by walking the spans up to the for loop's context first. This will not handle adjusting the location of macro variable expansions (e.g. for _ in $e), but this does adjust the context to match the for loops.

This ended up causing rust-lang/rust-clippy#16008. Clippy should be using a debug_assert rather than unreachable, but it still results in a bug either way.

rustbot · 2025-11-04T08:15:04Z

r? @davidtwco

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compiler/rustc_ast_lowering/src/expr.rs

rustbot · 2025-11-10T15:51:28Z

Some changes occurred in coverage tests.

cc @Zalathar

rustbot · 2025-11-10T15:51:30Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

davidtwco

r=me after removing commented line

View changes since this review

compiler/rustc_ast_lowering/src/expr.rs

davidtwco · 2025-11-11T16:42:51Z

@bors r+ rollup

bors · 2025-11-11T16:42:55Z

📌 Commit 84245da has been approved by davidtwco

It is now in the queue for this repository.

Adjust spans into the `for` loops context before creating the new desugaring spans. When lowering `for` loops, the spans for the `into_iter` call and the `Some` pattern used the span of the provided pattern and head expression. If either of those came from a different `SyntaxContext` this would result in some very strange contexts. e.g.: ```rust macro_rules! m { ($e:expr) => { { $e } } } for _ in m!(expr) {} ``` This would result in the `into_iter` call have a context chain of `desugar => m!() => root` which is completely nonsensical; `m!()` does not have a `for` loop. The `into_iter` call also ends up located at `{ $e }` rather than inside the `for _ in _` part. This fixes that by walking the spans up to the `for` loop's context first. This will not handle adjusting the location of macro variable expansions (e.g. `for _ in $e`), but this does adjust the context to match the `for` loops. --- This ended up causing rust-lang/rust-clippy#16008. Clippy should be using a `debug_assert` rather than `unreachable`, but it still results in a bug either way.

Rollup of 6 pull requests Successful merges: - #147753 (Suggest add bounding value for RangeTo) - #148080 ([rustdoc] Fix invalid jump to def macro link generation) - #148465 (Adjust spans into the `for` loops context before creating the new desugaring spans.) - #148500 (Update git index before running diff-index) - #148536 (cmse: add test for `async` and `const` functions) - #148819 (Remove specialized warning for removed target) r? `@ghost` `@rustbot` modify labels: rollup

Adjust spans into the `for` loops context before creating the new desugaring spans. When lowering `for` loops, the spans for the `into_iter` call and the `Some` pattern used the span of the provided pattern and head expression. If either of those came from a different `SyntaxContext` this would result in some very strange contexts. e.g.: ```rust macro_rules! m { ($e:expr) => { { $e } } } for _ in m!(expr) {} ``` This would result in the `into_iter` call have a context chain of `desugar => m!() => root` which is completely nonsensical; `m!()` does not have a `for` loop. The `into_iter` call also ends up located at `{ $e }` rather than inside the `for _ in _` part. This fixes that by walking the spans up to the `for` loop's context first. This will not handle adjusting the location of macro variable expansions (e.g. `for _ in $e`), but this does adjust the context to match the `for` loops. --- This ended up causing rust-lang/rust-clippy#16008. Clippy should be using a `debug_assert` rather than `unreachable`, but it still results in a bug either way.

Zalathar · 2025-11-11T23:02:16Z

Failed in rollup: #148829 (comment)

@bors r-

The coverage-run tests will need to be blessed with ./x test coverage --set=build.profiler=true --bless, as they are automatically skipped if the profiler runtime isn't enabled.

… and `into_iter` call spans.

Zalathar · 2025-11-12T01:16:09Z

It's unfortunate that coverage instrumentation is so sensitive to desugaring, but the new coverage output doesn't seem any worse than the current output, just different.

@bors r=davidtwco,Zalathar

bors · 2025-11-12T01:16:11Z

📌 Commit 76067c4 has been approved by davidtwco,Zalathar

It is now in the queue for this repository.

Adjust spans into the `for` loops context before creating the new desugaring spans. When lowering `for` loops, the spans for the `into_iter` call and the `Some` pattern used the span of the provided pattern and head expression. If either of those came from a different `SyntaxContext` this would result in some very strange contexts. e.g.: ```rust macro_rules! m { ($e:expr) => { { $e } } } for _ in m!(expr) {} ``` This would result in the `into_iter` call have a context chain of `desugar => m!() => root` which is completely nonsensical; `m!()` does not have a `for` loop. The `into_iter` call also ends up located at `{ $e }` rather than inside the `for _ in _` part. This fixes that by walking the spans up to the `for` loop's context first. This will not handle adjusting the location of macro variable expansions (e.g. `for _ in $e`), but this does adjust the context to match the `for` loops. --- This ended up causing rust-lang/rust-clippy#16008. Clippy should be using a `debug_assert` rather than `unreachable`, but it still results in a bug either way.

Rollup of 16 pull requests Successful merges: - #146627 (Simplify `jemalloc` setup) - #147753 (Suggest add bounding value for RangeTo) - #147832 (rustdoc: Don't pass `RenderOptions` to `DocContext`) - #147974 (Improve diagnostics for buffer reuse with borrowed references) - #148080 ([rustdoc] Fix invalid jump to def macro link generation) - #148465 (Adjust spans into the `for` loops context before creating the new desugaring spans.) - #148500 (Update git index before running diff-index) - #148531 (rustc_target: introduce Abi, Env, Os) - #148536 (cmse: add test for `async` and `const` functions) - #148770 (implement `feature(c_variadic_naked_functions)`) - #148780 (fix filecheck typos in tests) - #148819 (Remove specialized warning for removed target) - #148830 (miri subtree update) - #148833 (Update rustbook dependencies) - #148834 (fix(rustdoc): Color doctest errors) - #148841 (Remove more `#[must_use]` from portable-simd) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #148465 - Jarcho:for_span, r=davidtwco,Zalathar Adjust spans into the `for` loops context before creating the new desugaring spans. When lowering `for` loops, the spans for the `into_iter` call and the `Some` pattern used the span of the provided pattern and head expression. If either of those came from a different `SyntaxContext` this would result in some very strange contexts. e.g.: ```rust macro_rules! m { ($e:expr) => { { $e } } } for _ in m!(expr) {} ``` This would result in the `into_iter` call have a context chain of `desugar => m!() => root` which is completely nonsensical; `m!()` does not have a `for` loop. The `into_iter` call also ends up located at `{ $e }` rather than inside the `for _ in _` part. This fixes that by walking the spans up to the `for` loop's context first. This will not handle adjusting the location of macro variable expansions (e.g. `for _ in $e`), but this does adjust the context to match the `for` loops. --- This ended up causing rust-lang/rust-clippy#16008. Clippy should be using a `debug_assert` rather than `unreachable`, but it still results in a bug either way.

Rollup of 16 pull requests Successful merges: - rust-lang/rust#146627 (Simplify `jemalloc` setup) - rust-lang/rust#147753 (Suggest add bounding value for RangeTo) - rust-lang/rust#147832 (rustdoc: Don't pass `RenderOptions` to `DocContext`) - rust-lang/rust#147974 (Improve diagnostics for buffer reuse with borrowed references) - rust-lang/rust#148080 ([rustdoc] Fix invalid jump to def macro link generation) - rust-lang/rust#148465 (Adjust spans into the `for` loops context before creating the new desugaring spans.) - rust-lang/rust#148500 (Update git index before running diff-index) - rust-lang/rust#148531 (rustc_target: introduce Abi, Env, Os) - rust-lang/rust#148536 (cmse: add test for `async` and `const` functions) - rust-lang/rust#148770 (implement `feature(c_variadic_naked_functions)`) - rust-lang/rust#148780 (fix filecheck typos in tests) - rust-lang/rust#148819 (Remove specialized warning for removed target) - rust-lang/rust#148830 (miri subtree update) - rust-lang/rust#148833 (Update rustbook dependencies) - rust-lang/rust#148834 (fix(rustdoc): Color doctest errors) - rust-lang/rust#148841 (Remove more `#[must_use]` from portable-simd) r? `@ghost` `@rustbot` modify labels: rollup

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Nov 4, 2025

rustbot assigned davidtwco Nov 4, 2025

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Nov 4, 2025

Jarcho commented Nov 4, 2025

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Fix dbg_macro ICE when used iterated by for loop rust-lang/rust-clippy#16011

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Jarcho force-pushed the for_span branch from bb6fb61 to c87bb27 Compare November 10, 2025 14:38

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Jarcho force-pushed the for_span branch from c87bb27 to 5993789 Compare November 10, 2025 15:51

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Jarcho force-pushed the for_span branch from 5993789 to 6851dee Compare November 10, 2025 17:37

davidtwco approved these changes Nov 11, 2025

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Jarcho force-pushed the for_span branch from 6851dee to 84245da Compare November 11, 2025 14:49

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 Nov 11, 2025

GuillaumeGomez mentioned this pull request Nov 11, 2025

Rollup of 6 pull requests #148829

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Zalathar mentioned this pull request Nov 11, 2025

Rollup of 13 pull requests #148844

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bors 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 Nov 11, 2025

Adjust spans into the for loops context before creating the pattern…

76067c4

… and `into_iter` call spans.

Jarcho force-pushed the for_span branch from 84245da to 76067c4 Compare November 12, 2025 00:18

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 12, 2025

Zalathar mentioned this pull request Nov 12, 2025

Rollup of 16 pull requests #148851

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bors merged commit a2c8493 into rust-lang:main Nov 12, 2025
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rustbot added this to the 1.93.0 milestone Nov 12, 2025

Jarcho mentioned this pull request Nov 13, 2025

ICE dbg_macro rust-lang/rust-clippy#16008

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cuviper mentioned this pull request Jan 23, 2026

Code coverage reports wrong count of loop header #151554

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Adjust spans into the `for` loops context before creating the new desugaring spans.#148465

Adjust spans into the `for` loops context before creating the new desugaring spans.#148465
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